xG so far this season

[And Its Smith]

I am sure a lot of people are becoming more aware of xG and I am hoping someone who is well versed on it, and believes in it, can convince me that it isn't a pile of tosh! 

I listen to a lot of podcasts and read a lot about football and increasingly people are talking about xG as a more factual way to tell how well your team has played.  Some people seem to treat it as the 'justice league' i.e. the league without luck (I guess) and think it is more truthful than the league table.

We are 7th at the moment yet the xG table has us at 20th.  Other wild differences in the xG league are Swansea 14th (2nd in real life), Birmingham 24th (8th in real) and Stoke 4th (24th in real table).

Here are our results so far this season.  First of all the real result and then the xG result:

Leeds 1-3 loss......0.76 - 2.01 loss

Birmingham 1-1 draw...….0.62 - 1.36 win

QPR 2-0 win..….1.21 - 1.58 draw

Derby 2-1 win…...2.23 - 1.13 loss

Its the latest game that I would like people who believe in xG's opinion.  I watched the game at the ground and have seen it again since.  How does xG calculate that we deserved to lose that game?  xG seems to suggest that they deserved to win it because of the chances that fell to Tom Huddlestone and Tom Lawrence in the first half.  Giving those chances as high probability ones but then it gives Brownhill's goal as a 7% chance 

Is xG reliable and how on earth does it come up with its percentages for each chance? 

[IdliketoRogerMoore]

some People got way to much time on there hands to devise a new formulas and tables! 

Mid prefer to stick to the traditional table! 

Additional analysis is great but giving points based on someone’s opinion of a chance is going a bit far for me!

[Red DNA]

Complete over-analysis, some analytics are undoubtedly useful but I struggle to see what this offers other than an opinion based on ‘ifs’ and ‘buts’. 

Sometimes you get luck, other times you don’t, it’s life.

Football used to be such a simple game

 

[Major Isewater]

13 minutes ago, RedDave said:

I am sure a lot of people are becoming more aware of xG and I am hoping someone who is well versed on it, and believes in it, can convince me that it isn't a pile of tosh! 

I listen to a lot of podcasts and read a lot about football and increasingly people are talking about xG as a more factual way to tell how well your team has played.  Some people seem to treat it as the 'justice league' i.e. the league without luck (I guess) and think it is more truthful than the league table.

We are 7th at the moment yet the xG table has us at 20th.  Other wild differences in the xG league are Swansea 14th (2nd in real life), Birmingham 24th (8th in real) and Stoke 4th (24th in real table).

Here are our results so far this season.  First of all the real result and then the xG result:

Leeds 1-3 loss......0.76 - 2.01 loss

Birmingham 1-1 draw...….0.62 - 1.36 win

QPR 2-0 win..….1.21 - 1.58 draw

Derby 2-1 win…...2.23 - 1.13 loss

Its the latest game that I would like people who believe in xG's opinion.  I watched the game at the ground and have seen it again since.  How does xG calculate that we deserved to lose that game?  xG seems to suggest that they deserved to win it because of the chances that fell to Tom Huddlestone and Tom Lawrence in the first half.  Giving those chances as high probability ones but then it gives Brownhill's goal as a 7% chance 

Is xG reliable and how on earth does it come up with its percentages for each chance? 

There’s only one table that counts .

 

[handsofclay]

We obviously sat back in the second period v Derby and but for a wonder goal comfortably absorbed everything they threw at us.  I take it the fact they were 'allowed'  ascendancy in the second half means this xG has them down as being unlucky not to have won so gives them the win by 1.1 goals, a bigger margin than the 1 goal we ACTUALLY won by.

[BobBobSuperBob]

As a dinosaur I’m amazed at the complete modern obsession with stats

Useful in some small particular areas  but personally I’d rather trust my eyes , occasionally referring back to certain stats as a comparison to what I believe in seeing

And as for XG , As a Head Coach I’d much rather see a few mins of compilation of chances than take credence from a XG Score or map

IMHO

[cityexile]

I think what it ends up measuring is simply 'how good where you at taking your chances'. Birmingham for instance it shows us as winning, and most of us would have felt 'if only Afobe had buried one of those really good openings'. Equally against Derby I certainly came away from the ground thinking we were very clinical with our finishing. Interesting at that level, but cannot see that it gives you a 'better' real picture. There is no reason you should revert to the mean if your strikers are better finishers on average.

[And Its Smith]

2 minutes ago, handsofclay said:

We obviously sat back in the second period v Derby and but for a wonder goal comfortably absorbed everything they threw at us.  I take it the fact they were 'allowed'  ascendancy in the second half means this xG has them down as being unlucky not to have won so gives them the win by 1.1 goals, a bigger margin than the 1 goal we ACTUALLY won by.

On the contrary actually.  xG gives Derby no positives from their second half display as they created no clear cut chances.  

Their four big chances were all in the first half.  What I find weird is it doesn't give any importance (or doesn't seem too) for a good save or block tackle.  It only seems to concentrate on the attacking team.  I'm genuinely confused by it and want to understand it, even if I don't end up agreeing with it.

So far it seems everyone thinks its nonsense which is hard to argue with!!

[And Its Smith]

2 minutes ago, cityexile said:

I think what it ends up measuring is simply 'how good where you at taking your chances'. Birmingham for instance it shows us as winning, and most of us would have felt 'if only Afobe had buried one of those really good openings'. Equally against Derby I certainly came away from the ground thinking we were very clinical with our finishing. Interesting at that level, but cannot see that it gives you a 'better' real picture. There is no reason you should revert to the mean if your strikers are better finishers on average.

Weirdly it gives Afobe's two chances as exactly the same probability of a goal at 35% but then gives Nagy chance as 37%.  

[Mr Popodopolous]

It can be useful IMO, in showing underlying trends- for example I am quite sure we were outperforming our xG average in 2016/17 in the early stages- and this was reflected on the pitch. On the flipside, some underlying numbers during the awful run that LJ was lucky to survive showed an improvement.

Leeds however xG based should have finished if not top last season- had most shots on goal, some impressive numbers shots conceded, possession, dominance- yet finished 3rd and lost it towards the end.

In summary, think it is a useful guide to underlying form, performance level and perhaps a guide of future things to come- but that it has its limits.

[semblar]

Another point with this is whether you can actually apply this kind of statistical analysis to a single game with any expectation of accuracy. For a large number of games (not necessarily a whole season) I can see the approach, but I would not call four games a large enough pool to make a comparison with, especially given the change in personnel after the Leeds match 

[cidered abroad]

xG?

What is this mumbo jumbo?

No, please don't try to explain it to me. Leave me to my, old age, well past best before date, ignorance.

[And Its Smith]

3 minutes ago, Mr Popodopolous said:

It can be useful IMO, in showing underlying trends- for example I am quite sure we were outperforming our xG average in 2016/17 in the early stages- and this was reflected on the pitch. On the flipside, some underlying numbers during the awful run that LJ was lucky to survive showed an improvement.

Leeds however xG based should have finished if not top last season- had most shots on goal, some impressive numbers shots conceded, possession, dominance- yet finished 3rd and lost it towards the end.

In summary, think it is a useful guide to underlying form but that it has its limits.

My argument against it though would be that the xG percentages are complete nonsense which makes a mockery of the whole thing.

If the basis is flawed then it is useless.  How can they say we should have lost on Tuesday?  That's what I'm mainly trying to understand

[mozo]

19 minutes ago, RedDave said:

I am sure a lot of people are becoming more aware of xG and I am hoping someone who is well versed on it, and believes in it, can convince me that it isn't a pile of tosh! 

I listen to a lot of podcasts and read a lot about football and increasingly people are talking about xG as a more factual way to tell how well your team has played.  Some people seem to treat it as the 'justice league' i.e. the league without luck (I guess) and think it is more truthful than the league table.

We are 7th at the moment yet the xG table has us at 20th.  Other wild differences in the xG league are Swansea 14th (2nd in real life), Birmingham 24th (8th in real) and Stoke 4th (24th in real table).

Here are our results so far this season.  First of all the real result and then the xG result:

Leeds 1-3 loss......0.76 - 2.01 loss

Birmingham 1-1 draw...….0.62 - 1.36 win

QPR 2-0 win..….1.21 - 1.58 draw

Derby 2-1 win…...2.23 - 1.13 loss

Its the latest game that I would like people who believe in xG's opinion.  I watched the game at the ground and have seen it again since.  How does xG calculate that we deserved to lose that game?  xG seems to suggest that they deserved to win it because of the chances that fell to Tom Huddlestone and Tom Lawrence in the first half.  Giving those chances as high probability ones but then it gives Brownhill's goal as a 7% chance 

Is xG reliable and how on earth does it come up with its percentages for each chance? 

I think this is a fascinating post @RedDave. Firstly because I didn't know what our xg scores have been, but secondly because you raise a great point about the efficacy of this analysis. 

My intuition is that xg doesn't analyse who the chances fall to and a myriad of variables that are possibly not factored in such as did the ball fall kindly to the player on the their stronger foot, did it roll cleanly on the turf, was their sight of goal obstructed, how many seconds did they have to set themself etc etc. I need to learn more about what details are and aren't considered.

[Davefevs]

19 minutes ago, RedDave said:

I am sure a lot of people are becoming more aware of xG and I am hoping someone who is well versed on it, and believes in it, can convince me that it isn't a pile of tosh! 

I listen to a lot of podcasts and read a lot about football and increasingly people are talking about xG as a more factual way to tell how well your team has played.  Some people seem to treat it as the 'justice league' i.e. the league without luck (I guess) and think it is more truthful than the league table.

We are 7th at the moment yet the xG table has us at 20th.  Other wild differences in the xG league are Swansea 14th (2nd in real life), Birmingham 24th (8th in real) and Stoke 4th (24th in real table).

Here are our results so far this season.  First of all the real result and then the xG result:

Leeds 1-3 loss......0.76 - 2.01 loss

Birmingham 1-1 draw...….0.62 - 1.36 win

QPR 2-0 win..….1.21 - 1.58 draw

Derby 2-1 win…...2.23 - 1.13 loss

Its the latest game that I would like people who believe in xG's opinion.  I watched the game at the ground and have seen it again since.  How does xG calculate that we deserved to lose that game?  xG seems to suggest that they deserved to win it because of the chances that fell to Tom Huddlestone and Tom Lawrence in the first half.  Giving those chances as high probability ones but then it gives Brownhill's goal as a 7% chance 

Is xG reliable and how on earth does it come up with its percentages for each chance? 

As a stats man, I love my data....but you have to take it with a pinch of salt....especially if you’re going to use a 4 game sample.  Even 46 games is a statistically small sample.

xG is evolving its scoring accuracy, but until it can take lots of other things into account like, positioning if defenders, strong or weak foot, distance from ground, keeper’s save ratios from that spot etc etc, it’s always gonna be a “useful” metric but not the be-all and end-all.

What should we take from xG?

That Benik Afobe’s two one-on-ones v Brum are not gilt-edged chances, xG suggests both were a 1:5 ratio, so anyone saying a striker should take every one-on-one is not understanding that it is difficult.

A penalty is about 0.78 xG....so circa 1 in 5 is missed.

I do like the Stoke data....there is a guy, big Stoke analyst, who is trying to convince everyone that Stoke and Nathan Jones is about to turn everything around.  He might be right, but we know as football fans, when your team is on a downer, you concede all manner of shit goals, e.g. OGs, keeper errors, deflections etc that don’t reflect the balance of the game, and at the other end, keepers have worldies, the ball hits the wrong side of the post and bounces out rather than in etc.

Football will never be data driven, it’s too fluid a game....but data can be used smartly to make good / better decision either on recruitment or tactics.

[chinapig]

A reasonably good explanation, made more so by the fact that it is historic so you can see the extent to which it has any predictive capability.

https://www.telegraph.co.uk/football/2017/07/25/expected-goals-xg-does-show-man-city-should-win-premier-league/

Not that any sensible person relies on a single metric, or indeed solely on metrics, in any business. Though I often find that managers want the analytics to make decisions for them, there is no magic number.

[CiderCraig]

18 minutes ago, Major Isewater said:

There’s only one table that counts .

 

Is it this one? 

[mozo]

3 minutes ago, Davefevs said:

As a stats man, I love my data....but you have to take it with a pinch of salt....especially if you’re going to use a 4 game sample.  Even 46 games is a statistically small sample.

xG is evolving its scoring accuracy, but until it can take lots of other things into account like, positioning if defenders, strong or weak foot, distance from ground, keeper’s save ratios from that spot etc etc, it’s always gonna be a “useful” metric but not the be-all and end-all.

What should we take from xG?

That Benik Afobe’s two one-on-ones v Brum are not gilt-edged chances, xG suggests both were a 1:5 ratio, so anyone saying a striker should take every one-on-one is not understanding that it is difficult.

A penalty is about 0.78 xG....so circa 1 in 5 is missed.

I do like the Stoke data....there is a guy, big Stoke analyst, who is trying to convince everyone that Stoke and Nathan Jones is about to turn everything around.  He might be right, but we know as football fans, when your team is on a downer, you concede all manner of shit goals, e.g. OGs, keeper errors, deflections etc that don’t reflect the balance of the game, and at the other end, keepers have worldies, the ball hits the wrong side of the post and bounces out rather than in etc.

Football will never be data driven, it’s too fluid a game....but data can be used smartly to make good / better decision either on recruitment or tactics.

I love the data too, but you've done a great job there of explaining why xg is deeply flawed!

[And Its Smith]

5 minutes ago, Davefevs said:

As a stats man, I love my data....but you have to take it with a pinch of salt....especially if you’re going to use a 4 game sample.  Even 46 games is a statistically small sample.

xG is evolving its scoring accuracy, but until it can take lots of other things into account like, positioning if defenders, strong or weak foot, distance from ground, keeper’s save ratios from that spot etc etc, it’s always gonna be a “useful” metric but not the be-all and end-all.

What should we take from xG?

That Benik Afobe’s two one-on-ones v Brum are not gilt-edged chances, xG suggests both were a 1:5 ratio, so anyone saying a striker should take every one-on-one is not understanding that it is difficult.

A penalty is about 0.78 xG....so circa 1 in 5 is missed.

I do like the Stoke data....there is a guy, big Stoke analyst, who is trying to convince everyone that Stoke and Nathan Jones is about to turn everything around.  He might be right, but we know as football fans, when your team is on a downer, you concede all manner of shit goals, e.g. OGs, keeper errors, deflections etc that don’t reflect the balance of the game, and at the other end, keepers have worldies, the ball hits the wrong side of the post and bounces out rather than in etc.

Football will never be data driven, it’s too fluid a game....but data can be used smartly to make good / better decision either on recruitment or tactics.

Thanks for this.  Confirming to me that it is not really worth looking at.  I've not seen Stoke this season but I get the impression that if Butland was even playing to 75% of his capabilities they would be a lot higher. 

The Derby game and what you have written have confirmed my suspicion that xG isn't good enough a model to put faith in.  I guess the only thing it can be used for is to show you how many chances you are creating as a team, and how good those chances are.  To use to it say that Derby should have won is nonsense as Bentley's save and Kalas tackle in the first half are two of the big reasons that we won and cant just be ignored. 

[Davefevs]

3 minutes ago, RedDave said:

My argument against it though would be that the xG percentages are complete nonsense which makes a mockery of the whole thing.

If the basis is flawed then it is useless.  How can they say we should have lost on Tuesday?  That's what I'm mainly trying to understand

That is partly the problem, I don’t think the stats purists are saying we should have lost on Tuesday.  However stats amateurs (like myself) are using one metric to try to do just that.

To simplify, If we take a shot from the edge of the box centrally, it will have a low xG, because of all of the goals from that spot are added up and divided by the total of the shots.  Let’s say the xG was 0.1.  However if on Tuesday that shot from that spot was an open goal because Afobe had nipped the ball around the onrushing keeper, you’d expect him to roll it into the net 99/100.  The xG isn’t sophisticated enough to know that, so it’s still counted as 0.1.

Now play that out with Weimann’s goal.  It doesn’t know that the keeper is on his arse, no one is challenging him, so in real terms it was a gilt-edged chance.  But in xG it’s a left foot shot from 6 yards.

[And Its Smith]

3 minutes ago, Davefevs said:

That is partly the problem, I don’t think the stats purists are saying we should have lost on Tuesday.  However stats amateurs (like myself) are using one metric to try to do just that.

To simplify, If we take a shot from the edge of the box centrally, it will have a low xG, because of all of the goals from that spot are added up and divided by the total of the shots.  Let’s say the xG was 0.1.  However if on Tuesday that shot from that spot was an open goal because Afobe had nipped the ball around the onrushing keeper, you’d expect him to roll it into the net 99/100.  The xG isn’t sophisticated enough to know that, so it’s still counted as 0.1.

Now play that out with Weimann’s goal.  It doesn’t know that the keeper is on his arse, no one is challenging him, so in real terms it was a gilt-edged chance.  But in xG it’s a left foot shot from 6 yards.

So does it just look at the shot?  If so that is pretty poor.

Weimann still had a bit to do and his turn put the keeper on his arse.  It gives it as a 70% chance which seems high.  He still had a bit of work to do. 

Do you listen to Not The Top 20 podcast?  Its a superb listen but they put a lot of faith in xG 

[phantom]

17 minutes ago, cidered abroad said:

xG?

What is this mumbo jumbo?

No, please don't try to explain it to me. Leave me to my, old age, well past best before date, ignorance.

I'm glad that it is not just me !

I have no idea what xG is either. . . 

[WarksRobin]

How’s the packing?

[BobBobSuperBob]

8 minutes ago, Davefevs said:

That is partly the problem, I don’t think the stats purists are saying we should have lost on Tuesday.  However stats amateurs (like myself) are using one metric to try to do just that.

To simplify, If we take a shot from the edge of the box centrally, it will have a low xG, because of all of the goals from that spot are added up and divided by the total of the shots.  Let’s say the xG was 0.1.  However if on Tuesday that shot from that spot was an open goal because Afobe had nipped the ball around the onrushing keeper, you’d expect him to roll it into the net 99/100.  The xG isn’t sophisticated enough to know that, so it’s still counted as 0.1.

Now play that out with Weimann’s goal.  It doesn’t know that the keeper is on his arse, no one is challenging him, so in real terms it was a gilt-edged chance.  But in xG it’s a left foot shot from 6 yards.

I remember LJ at the first fans forum he did talking about data and stating after each game he received a pack which he indicated was a couple of inches thick  to digest

id be fascinated to know how much weight he puts to this data and whether as his experience grows , if he’s changed in the amount he looks at or digests

I fear, due to an obvious interest in learning ,  he may or may have been be vulnerable to data overload  

He grew up playing in a professional academy , has been in the game his whole life, the added bonus of his Dad being in management , played in hundreds and seen thousands of games ..... I’d be amazed if theirs many stats that would tell him , JM , DH something , or certainly anything significant , they hadn’t already noticed or were aware of 

[Davefevs]

2 minutes ago, RedDave said:

So does it just look at the shot?  If so that is pretty poor.

Weimann still had a bit to do and his turn put the keeper on his arse.  It gives it as a 70% chance which seems high.  He still had a bit of work to do. 

Do you listen to Not The Top 20 podcast?  Its a superb listen but they put a lot of faith in xG 

It has a bit more info than the simplicity in which I explain it.

I have started listening to NTT20, and although I get more intel about Lg1/2 than I would from watching Quest highlights and following our loanee player club’s twitter, I find them a bit “superior” in their views.  Maybe because I don’t necessarily agree with some of their thoughts / comments.

There are a few data people on twitter who are excellent, but there are some who are no better than those ill-informed ex-pro pundits....using stats as the be-all and end-all....you wonder if they are watching the game.

I had a friendly argument on Twitter with a Brum guy (Gabriel Sutton), who’s quite respected.  In our 1-1 draw his vlog said it was an even game and a draw was fair, they had the better of the play, we had the better chances.  I then looked at the player ratings and Brum were all 7/8/9 - totalled something like 85, ours were all 6s/odd-7, totalled something like 67.

I challenged his could all the Brum boys be so high and ours so low in an even game.

Its all a bit of bollox in some regards.  Use data, fine, but trust your eyes too.

[And Its Smith]

3 minutes ago, Davefevs said:

It has a bit more info than the simplicity in which I explain it.

I have started listening to NTT20, and although I get more intel about Lg1/2 than I would from watching Quest highlights and following our loanee player club’s twitter, I find them a bit “superior” in their views.  Maybe because I don’t necessarily agree with some of their thoughts / comments.

There are a few data people on twitter who are excellent, but there are some who are no better than those ill-informed ex-pro pundits....using stats as the be-all and end-all....you wonder if they are watching the game.

I had a friendly argument on Twitter with a Brum guy (Gabriel Sutton), who’s quite respected.  In our 1-1 draw his vlog said it was an even game and a draw was fair, they had the better of the play, we had the better chances.  I then looked at the player ratings and Brum were all 7/8/9 - totalled something like 85, ours were all 6s/odd-7, totalled something like 67.

I challenged his could all the Brum boys be so high and ours so low in an even game.

Its all a bit of bollox in some regards.  Use data, fine, but trust your eyes too.

Exactly.  

Agree that they are a bit superior. Better than The Second Tier podcast though who just seem clueless. 

I think a lot of people will use stats so they can have opinions on games they haven’t seen.

i am sure a lot of people over the age of 30 has watched City over 300 times and probably watched 1000+ games either live or on TV.  Eyes beat stats any day 

[the red rules]

40 minutes ago, cidered abroad said:

xG?

What is this mumbo jumbo?

No, please don't try to explain it to me. Leave me to my, old age, well past best before date, ignorance.

Mumbo Jumbo to me too. But I must admit to looking it up reading this thread and trying to feel not past it.              Wish I hadn't bothered, you're not missing much remaining ignorant.

 

 

[Davefevs]

9 minutes ago, RedDave said:

Exactly.  

Agree that they are a bit superior. Better than The Second Tier podcast though who just seem clueless. 

I think a lot of people will use stats so they can have opinions on games they haven’t seen.

i’m amazed at the “detailed” opinions of some people on so many players.  The guy I refer to above was suggesting Tommy Rowe would be better suited to LCB than Nathan Baker.  FFS!!  I have a pretty photographic memory, but you’d have to consume a helluva lot of games to really have any real say in how good a player is or isn’t, and then suggest he could play a position better than someone else, especially as he’s never played LCB!  I suspect a lot have played a lot of FM / FIFA.

i am sure a lot of people over the age of 30 has watched City over 300 times and probably watched 1000+ games either live or on TV.  Eyes beat stats any day 

The problem is that our memory starts to fade!!

 

[chinapig]

6 minutes ago, RedDave said:

Exactly.  

Agree that they are a bit superior. Better than The Second Tier podcast though who just seem clueless. 

I think a lot of people will use stats so they can have opinions on games they haven’t seen.

i am sure a lot of people over the age of 30 has watched City over 300 times and probably watched 1000+ games either live or on TV.  Eyes beat stats any day 

The problem with your eyes is that they are connected to your brain!

We are all subject to bias so if we have a preconceived opinion of a player or team we are likely to ignore evidence that doesn't support our opinion. So if we want to be objective we need more than just the evidence of our own eyes.

Not a big deal if you are just an interested observer but more so if you are responsible for making decisions.

[cidered abroad]

21 minutes ago, RedDave said:

Exactly.  

Agree that they are a bit superior. Better than The Second Tier podcast though who just seem clueless. 

I think a lot of people will use stats so they can have opinions on games they haven’t seen.

i am sure a lot of people over the age of 30 has watched City over 300 times and probably watched 1000+ games either live or on TV.  Eyes beat stats any day 

I've never counted them  but it could be over 2,000.

My problem now is that I clearly remember fifty years ago but yesterday is a bit foggy.

How did we get on Tuesday evening at Derby? Stuffed again and probably had Norman Hunter red carded for chopping Franny Lee?

[David Brent]

I love stats and analysis and can see the benefits to LJ and the coaching team but any alternative table means nothing

[Davefevs]

https://wizardsofdrivel.com/2019/08/23/things-can-only-get-better-why-stoke-should-stick-with-nathan-jones/amp/?__twitter_impression=true

All very desperate

[Ohbasso]

I’d never bother using xg to decide what the league table should look like but it can be useful for showing if a team is getting worse results than their performance suggests or vice versa. I only ever really use the xg graphs that show an overview of the game I find these give you a much better idea of how a games panned out rather than the traditional shots/shots on target/corner stats. They obviously still won’t be as good as watching a game but alongside the highlights they can give you a reasonable view of what’s happened.

 

[And Its Smith]

18 minutes ago, Ohbasso said:

I’d never bother using xg to decide what the league table should look like but it can be useful for showing if a team is getting worse results than their performance suggests or vice versa. I only ever really use the xg graphs that show an overview of the game I find these give you a much better idea of how a games panned out rather than the traditional shots/shots on target/corner stats. They obviously still won’t be as good as watching a game but alongside the highlights they can give you a reasonable view of what’s happened.

 

How is it useful to show if a teams performances are better than the results though if the very information to decide xG is flawed? 

Surely Kalas’s block on Tuesday to stop a near certain goal is part of our overall performance. Yet xG ignores it

[cider-manc]

I'm pretty sure that this sort of thing has only been introduced thanks to Sky Sports needing something to talk about on their 24 hour news channel.

[Ohbasso]

2 minutes ago, RedDave said:

How is it useful to show if a teams performances are better than the results though if the very information to decide xG is flawed? 

Surely Kalas’s block on Tuesday to stop a near certain goal is part of our overall performance. Yet xG ignores it

Yeah it’s far from perfect and you’d be daft to base your view of a match entirely on xg. Like I said the graphs like I posted above are much better than the traditional stats you normally see after a match and are good for showing spells of pressure and whether a game was end to end or attack v defence etc.

[Numero Uno]

This xG malarkey can not possibly take tactics into account. Second half at Derby we are 2-0 up and are not going to chase the game in any way. As for chances being saved by Goalkeepers that’s what they are paid well to do!!! Baker heading everything that moved......that’s his job. It clearly doesn’t work on the basis that a team doing what it’s instructed to do and win the game deserves to win it!! If you miss sitters you don’t deserve anything and perhaps it shows a lack of ability.

Sounds like software written for the Gas Hordes to cry into their cornflakes over...we deserved to win, we deserve a new ground blah blah blah

[Davefevs]

10 minutes ago, Ohbasso said:

Yeah it’s far from perfect and you’d be daft to base your view of a match entirely on xg. Like I said the graphs like I posted above are much better than the traditional stats you normally see after a match and are good for showing spells of pressure and whether a game was end to end or attack v defence etc.

Yep, I use the Experimental 361 xG charts too....useful to see that City’s chances were less often, but more clear.  If you look at the Statszone view too.

Derby had 11 shots outside the box....speculative in xG terms!

I think we will see a lot of this, with our players getting blocks because our 3 CBs will cover a lot of space in front of goal.

[JamesBCFC]

2 hours ago, RedDave said:

My argument against it though would be that the xG percentages are complete nonsense which makes a mockery of the whole thing.

If the basis is flawed then it is useless.  How can they say we should have lost on Tuesday?  That's what I'm mainly trying to understand

xG is about how likely a goal is from a certain chance created.

7% for Brownhills goal isn't that low when you consider how often people blaze over from there

I believe a penalty has an xG of 0.7, because it's roughly how many penalties are scored.

So Lawrence's chance from about 5 yards out will have had a very high xG. Some xG models take into account where the defenders are and others don't, so you could see quite a variation in xG numbers for a game just from looking at different models.

[Fpcity]

I was thinking the other day it's a load of bollocks. You can't predict football. 

 

[Mr Popodopolous]

5 minutes ago, Numero Uno said:

This xG malarkey can not possibly take tactics into account. Second half at Derby we are 2-0 up and are not going to chase the game in any way. As for chances being saved by Goalkeepers that’s what they are paid well to do!!! Baker heading everything that moved......that’s his job. It clearly doesn’t work on the basis that a team doing what it’s instructed to do and win the game deserves to win it!! If you miss sitters you don’t deserve anything and perhaps it shows a lack of ability.

Sounds like software written for the Gas Hordes to cry into their cornflakes over...we deserved to win, we deserve a new ground blah blah blah

Dunno- maybe expected goals isn't the best example of it but data and analytics really on the rise in football. For better or worse- xG is just one element of this.

https://bleacherreport.com/articles/2659234-epl-2030-a-data-driven-future-football-dystopia-or-beautiful-holographic-game

The above is a bit of fun but also informative.

http://outsideoftheboot.com/2016/07/21/rise-of-data-analytics-in-football/

Could reach new levels of micromanagement by coaches and management of players moving forward, but at the expense of the excitement, the flair- the unexpected.

Football has been a slow adapter to this sort of thing, but over the next decade it'll be interesting to see how it all develops.

[JamesBCFC]

27 minutes ago, RedDave said:

How is it useful to show if a teams performances are better than the results though if the very information to decide xG is flawed? 

Surely Kalas’s block on Tuesday to stop a near certain goal is part of our overall performance. Yet xG ignores it

It doesn't.

xG doesn't tell you how well a team has played.

If an opportunity with an xG rating of 0.9 is missed it could be a save or the ball hit against the post from a yard out- xG doesn't say that it's a bad miss or a fantastic block, just that there was a chance.

Just like with Brownhills goal. The fact it had an xG of 0.07 and was scored doesn't mean there was a goalkeeping howler, or that Brownhill scored a worldie. Just that goals in that situation are uncommon.

[Numero Uno]

It’s another tool for certain people to beat the team with on the Matchday Thread next time we go a goal down........or “we were lucky, xG said so!!”.

[Numero Uno]

3 minutes ago, Mr Popodopolous said:

Dunno- maybe expected goals isn't the best example of it but data and analytics really on the rise in football. For better or worse- xG is just one element of this.

https://bleacherreport.com/articles/2659234-epl-2030-a-data-driven-future-football-dystopia-or-beautiful-holographic-game

The above is a bit of fun but also informative.

http://outsideoftheboot.com/2016/07/21/rise-of-data-analytics-in-football/

Could reach new levels of micromanagement by coaches and management of players moving forward, but at the expense of the excitement, the flair- the unexpected.

Football has been a slow adapter to this sort of thing, but over the next decade it'll be interesting to see how it all develops.

The problem comes when you become reliant on this stuff. GJ used to bang on about Prozone stats all the time from my hazy memory. Even if you do agree with the principle of how it or other analyticals out there work (and LJ might, who knows) you have to trust what you SEE in conjunction with it. If it identifies a minor tweak you need to make then great but reliance on this stuff is dangerous imo.

[Numero Uno]

8 minutes ago, JamesBCFC said:

It doesn't.

xG doesn't tell you how well a team has played.

If an opportunity with an xG rating of 0.9 is missed it could be a save or the ball hit against the post from a yard out- xG doesn't say that it's a bad miss or a fantastic block, just that there was a chance.

Just like with Brownhills goal. The fact it had an xG of 0.07 and was scored doesn't mean there was a goalkeeping howler, or that Brownhill scored a worldie. Just that goals in that situation are uncommon.

How is that 0.07 judged? The probability of Josh Brownhill sticking that chance in the onion bag or does it include League 2 players. For example the probability of De Bruyne putting that away would be nearer 40% or probably higher on reflection than 7% imo.

[And Its Smith]

8 minutes ago, JamesBCFC said:

It doesn't.

xG doesn't tell you how well a team has played.

If an opportunity with an xG rating of 0.9 is missed it could be a save or the ball hit against the post from a yard out- xG doesn't say that it's a bad miss or a fantastic block, just that there was a chance.

Just like with Brownhills goal. The fact it had an xG of 0.07 and was scored doesn't mean there was a goalkeeping howler, or that Brownhill scored a worldie. Just that goals in that situation are uncommon.

I guess my issue might be more with the way that pundits are talking about xG.  As in saying one team deserved to win as they had a higher xG.

 

[JamesBCFC]

1 minute ago, Numero Uno said:

How is that 0.07 judged? The probability of Josh Brownhill sticking that chance in the onion bag or does it include League 2 players. For example the probability of De Bruyne putting that away would be nearer 40% than 7% imo.

Can't be certain but think it's essentially all shots from that area and all goals from that area.

There's an almost endless amount of things that can go into an xG model

This could be worth a read (although it loaded up horribly on my phone)

http://alexrathke.net/expected-goals/

So on some models things like the weight of the pass can come into play.

 

xG is still relatively new and I expect over the next few years the models will get more and more refined, perhaps even to the point where there's a different xG for each of the divisions as more data becomes available.

[Unan]

To me, all xG says is how clinical your strikers are, you aren’t in the wrong position in the table because your striker can’t hit a barn door. I seem to recall we had quite a high xG last season but, for all his positives, Fam isn’t that stone cold clinical striker like others.

[Numero Uno]

4 minutes ago, JamesBCFC said:

Can't be certain but think it's essentially all shots from that area and all goals from that area.

There's an almost endless amount of things that can go into an xG model

This could be worth a read (although it loaded up horribly on my phone)

http://alexrathke.net/expected-goals/

So on some models things like the weight of the pass can come into play.

 

xG is still relatively new and I expect over the next few years the models will get more and more refined, perhaps even to the point where there's a different xG for each of the divisions as more data becomes available.

A lot needs to go into a model like that to make it accurate. Take Brownhill’s goal at Derby......he’s running into a perfectly weighted ball, he’s in total control to the point he shouts Weimann to leave it...he knows he’s going to be ripping the onion bag (as much as you can know!!) so you could argue that the percentage chance of scoring should be far higher than 7% compared to being in exactly the same position with a defender closing him and more weight on the pass?

As you say if people start believing in it they will have to refine it a lot further. But for me I wouldn’t use it to say your 7th position in the league is “lucky”....no way.

[Unan]

I expect a city the size of Bristol to have 2 competitive league teams, I expect a 18 year old Monaco wonder kid to go to a prem team. Fortunately expectations aren’t reality.

[Unan]

The more I think about it the more I disagree with it. A player like Fam will hold the ball up well, bring other forwards in to play & create chances for others but will miss a lot himself, giving us a high xG and a low actual goals ratio. Whereas, a player like Tammy won’t do any of that work that Fam is so good at, but when he has a chance he’ll put it away, giving him a low xG but a high actual goals ratio. On paper you’d obviously think the low xG/high aG was the far better option but obviously that isn’t the case.

(I’m not actually comparing Tammy/Fammy, but players of their mould)

[JamesBCFC]

23 minutes ago, Numero Uno said:

A lot needs to go into a model like that to make it accurate. Take Brownhill’s goal at Derby......he’s running into a perfectly weighted ball, he’s in total control to the point he shouts Weimann to leave it...he knows he’s going to be ripping the onion bag (as much as you can know!!) so you could argue that the percentage chance of scoring should be far higher than 7% compared to being in exactly the same position with a defender closing him and more weight on the pass?

As you say if people start believing in it they will have to refine it a lot further. But for me I wouldn’t use it to say your 7th position in the league is “lucky”....no way.

That I agree on, particularly so early in the season.

What xG could be used with is other statistics (and eyes) to suggest whether a team is underperforming.

An example being Juventus a couple of seasons ago. Their xG was 2+ higher that their opponents frequently, but they drew or lost a fair number of their first 12 games.

So such a consistent amount of games where they scored well below their xG says that their results aren't always reflective of the performances. They then went and steamrollered their way through the rest of the season and won the title at a canter.

 

A lot of statistics in football is knowing what to use and when.

Do multiple different stats give the same impression of a game, etc.

[Davefevs]

3 hours ago, Unan said:

The more I think about it the more I disagree with it. A player like Fam will hold the ball up well, bring other forwards in to play & create chances for others but will miss a lot himself, giving us a high xG and a low actual goals ratio. Whereas, a player like Tammy won’t do any of that work that Fam is so good at, but when he has a chance he’ll put it away, giving him a low xG but a high actual goals ratio. On paper you’d obviously think the low xG/high aG was the far better option but obviously that isn’t the case.

(I’m not actually comparing Tammy/Fammy, but players of their mould)

This is Fammy v Tammy last season, adjusted to remove penalties.  Think Fam had 2, Tammy 7.  Something like that.

What does this show us?

Chart 1- Tammy scores more goals (non pens) per 90, but Fam is still above average for all players that played as strikers last season.

Chart 2 - Tammy gets more / better chances per 90.

Chart 3 - they actually take their chances at a similar rate (so give Fam the types of chances that Tammy gets, and he might score as many).

Interesting isn’t it.

[Unan]

2 hours ago, Davefevs said:

This is Fammy v Tammy last season, adjusted to remove penalties.  Think Fam had 2, Tammy 7.  Something like that.

What does this show us?

Chart 1- Tammy scores more goals (non pens) per 90, but Fam is still above average for all players that played as strikers last season.

Chart 2 - Tammy gets more / better chances per 90.

Chart 3 - they actually take their chances at a similar rate (so give Fam the types of chances that Tammy gets, and he might score as many).

Interesting isn’t it.

I was thinking Tammy wasn’t a great example as he was in that Villa team. Saying that I can’t believe how many changes he missed! A relatively poor conversion rate all things considering.

[Lrrr]

8 hours ago, Unan said:

To me, all xG says is how clinical your strikers are, you aren’t in the wrong position in the table because your striker can’t hit a barn door. I seem to recall we had quite a high xG last season but, for all his positives, Fam isn’t that stone cold clinical striker like others.

This, xG helps when looking at strikers and how well they finish chances, in the chart below the line runs at xG and goals per 90 being equal. In recruitment it can help find under valued strikers.

[Nogbad the Bad]

xG- puts me in mind of that long time American poster who came over to watch the City v Hull play off final.

He was put up over night by someone on the forum iirc?

Got it, x3widRacin, not very active on here since and not at all since January last year.

Can only imagine witnessing a big occasion City let down might have gradually cooled his BCFC ardour!?

Not used to it like the rest of us!!

[Southport Red]

On 23/08/2019 at 10:48, cidered abroad said:

xG?

What is this mumbo jumbo?

No, please don't try to explain it to me. Leave me to my, old age, well past best before date, ignorance.

Was about to say the sane. WTF when it’s at home, is XG?

[BobBobSuperBob]

8 minutes ago, Southport Red said:

Was about to say the sane. WTF when it’s at home, is XG?

‘expected goals’