XG?

[Mr Popodopolous]

1 hour ago, Maltshoveller said:

XG is a total waste of time

The only thing that matters is what happened in a game

Not what coulda woulda shoulda 

It predicted our decline in 2016, relative decline in 2019 and decline in 2020 from a strong start however.

Take the below. 30 pts from 17 is quite impressive. However we we know we were lucky in a number of those games..the XG reflects!

Lo and behold we did decline. Quite sharply!

Edited August 28, 2023 by Mr Popodopolous

[TV Tom]

In Brightons case they had

80% possession,

25 shots to 12,

736 passes to 199 (not that i'm a fan of that stat')

17 corners to four

 

These stats tell me that in all likelihood Brighton should of won and probably would do 4 times out of 5 yet XG says differently by quite a considerable margin all though in fairness it says that WHU should of won 3-1 which remarkably is exactly what they did !!!!!

 

[Maltshoveller]

3 minutes ago, TV Tom said:

In Brightons case they had

80% possession,

25 shots to 12,

736 passes to 199 (not that i'm a fan of that stat')

17 corners to four

 

These stats tell me that in all likelihood Brighton should of won and probably would do 4 times out of 5 yet XG says differently by quite a considerable margin all though in fairness it says that WHU should of won 3-1 which remarkably is exactly what they did !!!!!

 

So what it tells you is

That if you score 3 and only let in 1 

you will win 100% of the time

[downendcity]

Only one stat that matters - the final score.

As they say in golf, at the end of the round it's not the how that counts, just the how many

[ExiledAjax]

2 minutes ago, downendcity said:

Only one stat that matters - the final score.

As they say in golf, at the end of the round it's not the how that counts, just the how many

How do you score goals?

How do you make a birdie on the golf course?

[Mr Popodopolous]

2019. While this model is a bit questionable, it also shows some patterns that were borne out ie our form was vastly exceeding our performance level. I don't agree with the 14 Point difference but it was quite prescient for a few sides.

At the other end, Leeds were comfortably the best side under that model..and so it proved.

Brentford were 17th after 11 games in real time yet the model fairly accurately forecast that they would be up nearr the top if they kept playing as they were.

Charlton also fell away majorly by the end of the season. Their 18 pts from 11 games did not reflect and was unsustainable on that Performance level.

Otoh Stoke there was a huge mismatch!

Edited August 28, 2023 by Mr Popodopolous

[johnbytheriver]

14 hours ago, !james said:

https://statsbomb.com/soccer-metrics/expected-goals-xg-explained/

I have just tried to read this! I must be too old! What utter Bollocks!

 

[bearded_red]

Almost all professional clubs use it in analysis of games and scouting of players.

Professional gamblers made a lot of money using it before it got into the mainstream.

Must be bollocks though, otib said so.

[Alessandro]

43 minutes ago, ExiledAjax said:

Yes. That's what xG says.

0.2 for Williams, 0.12 for Knight's header. So xG reckons Williams shot would be a goal 1 in 5 times, and Knight's about 1 in 8. So yes, Williams' chance was quite a bit better.

xG has taught me that we as fans tend to greatly underestimate how hard it is to score a goal.

Really surprised by those stats (an open goal at 12 yards and a free header at 5 yards) but there we go, who am I to argue with the computers!! 

Edited August 28, 2023 by Alessandro

[cidercity1987]

Said it before , il say it again.

Don't trust XG and haven't since Diedhiou tap in from a barely trickling cross on the goal line at Fulham was only about 0.6XG. Great team move though

[ExiledAjax]

13 minutes ago, Alessandro said:

Really surprised by those stats (an open goal at 12 yards and a free header at 5 yards) but there we go, who am I to argue with the computers!! 

Both are decent, even good, chances. The average xG value for any shot is about 0.1, many, many, many shots are taken that have a 0.02, 0.03 chance of being scored.

Against that, even Knight's 0.12 chance is very good, about 20% better than the average shot. Williams' chance was about twice as likely to be a goal than the average shot taken. Good chances.

[Gurney]

No statistic in isolation tells the whole story, but in terms of being indicative of how good a team is performing in the grand scale of things, xG is amongst the best.

[Davefevs]

3 hours ago, Silvio Dante said:

I’m no lover of xG - as I said, I’m not sure it shows you anything you don’t see yourself. But again, it’s useful to give meat to the bones of an opinion.

I think it’s clear some people watch a very different game!

3 hours ago, Alessandro said:

What I don’t understand about the XG here is how many factors taken into consideration:

Is no.4 the chance Joe missed?

Let’s take that for example - it was 0.20 - so XG is saying only 2/10 times a player will hit the target from 12 yards out?! 
 

That’s surely wrong - so can only presume 0.20 is the 2/10 chance of scoring if the goalkeeper is in the right place - in this case it’s clearly not taken into consideration that the keeper is flat on the floor out of the place and the goal is gaping?!

Also out of interest - if you have time, don’t worry if not - what was the XG on Knights header in the second half from the corner? Thank you! 

No, it’s saying 2/10 Williams scores.

If we go back to that chance, ball rebounding to him at pace on the bounce, defender on the line, other players blocking any shot route to the other half of the goal, etc, etc.. it wasn’t an open goal.

Knight’s header from the corner - 0.12 (1/8 ish).  Headers are statistically less likely to be scored than shots with feet.

1 hour ago, RoystonFoote'snephew said:

I'd rather base the likelihood of scoring on who's taking the shot, for example Bas Savage might of hit the target once in 50 attempts, Oli Gunnar Soljaer 9 out of every 10 

That’s where something called “post shot xG” comes in.  Basically does a similar calculation to xG but based on where the shot ends up, speed, etc.

A 10 yard dribbler to the centre of the goal where there keeper throws his cap on it will get a very low PSxG.

A 10 yard thunderbastard into “top bins” with the keeper nowhere near it will get a very high PSxG.

The likes of Harry Kane has a much higher PSxG than xG because he finds the target and corners with regularity.

So xG is getting more sophisticated as new things are added.

1 hour ago, ExiledAjax said:

xG has taught me that we as fans tend to greatly underestimate how hard it is to score a goal.

Indeed, a half chance in most fans eyes does not have an xG anywhere near 0.5!!!

A gilt-edged chance in most fans eyes probably has an xG between 0.2-0.3.

Unless it’s a pen 0.76.

[Davefevs]

1 hour ago, TV Tom said:

In Brightons case they had

80% possession,

25 shots to 12,

736 passes to 199 (not that i'm a fan of that stat')

17 corners to four

 

These stats tell me that in all likelihood Brighton should of won and probably would do 4 times out of 5 yet XG says differently by quite a considerable margin all though in fairness it says that WHU should of won 3-1 which remarkably is exactly what they did !!!!!

 

Look at the shot map!  Several of Brighton’s shots were speculative 25 yarders.

[ExiledAjax]

1 minute ago, Davefevs said:

I think it’s clear some people watch a very different game!

No, it’s saying 2/10 Williams scores.

If we go back to that chance, ball rebounding to him at pace on the bounce, defender on the line, other players blocking any shot route to the other half of the goal, etc, etc.. it wasn’t an open goal.

Knight’s header from the corner - 0.12 (1/8 ish).  Headers are statistically less likely to be scored than shots with feet.

That’s where something called “post shot xG” comes in.  Basically does a similar calculation to xG but based on where the shot ends up, speed, etc.

A 10 yard dribbler to the centre of the goal where there keeper throws his cap on it will get a very low PSxG.

A 10 yard thunderbastard into “top bins” with the keeper nowhere near it will get a very high PSxG.

The likes of Harry Kane has a much higher PSxG than xG because he finds the target and corners with regularity.

So xG is getting more sophisticated as new things are added.

Indeed, a half chance in most fans eyes does not have an xG anywhere near 0.5!!!

A gilt-edged chance in most fans eyes probably has an xG between 0.2-0.3.

Unless it’s a pen 0.76.

Even pens I reckon most fans would guess that 9/10 are scored rather than the 7.6/10.

Only on Saturday the BBC ran a little piece during the text comms on the Sheff Utd/Man City game that said "Man City have only scored 7 of their last ten penalties". The implication being that this was a great failure, was shockingly bad etc...it's not, it's only slightly below par.

[Davefevs]

[MarcusX]

Some people have done a really good job here of explaining how it works, why it’s useful and what you can (and can’t) take from it

Its a bit rude for others to just dismiss it as bollocks, likely because they either don’t understand or just because it doesn’t match what they think they’ve seen.

@IAmNickexplained it really well with the comparison to the thoughts we have. Our thoughts are impacted by bias though.

[transfer reader]

48 minutes ago, Alessandro said:

Really surprised by those stats (an open goal at 12 yards and a free header at 5 yards) but there we go, who am I to argue with the computers!! 

There's probably 3 or 4 times a game where someone gets a free or near free header, yet we aren't seeing 2-2 draws up and down the country where all the goals are headers scored like that.

This is where it comes to our own biases, the xG strips that away and applies data from what's actually happened.

I'm sure we've all been at games where we've said something along the lines of "we can't keep letting x club get free headers/x opportunity or they'll score".

That's our own internal xG at work, we just haven't applied numbers to it.

 

From Opta, 38% of non penalty "big chances" are scored, for  other non-big chances from inside the box, Opta tells us that there is a 7% chance of a goal, 0.07 xG

So an xG of 0.2 is pretty decent, with people scoring from similar chances about 3x more often than the average chance inside the penalty area.

Knights header being 0.12 says it was a better than average chance

[transfer reader]

22 minutes ago, Davefevs said:

This says to me (not watched the game or any highlights of it) the 2 Ward-Prowse chances on 19 mins were huge, very rare to see open play xG of over 0.35 for a single shot

[Davefevs]

4 minutes ago, transfer reader said:

This says to me (not watched the game or any highlights of it) the 2 Ward-Prowse chances on 19 mins were huge, very rare to see open play xG of over 0.35 for a single shot

Defender makes a great block on six-yard line from JWP chance with keeper beaten, rebound falls to JWP for open goal on the angle. Icon 3 isn’t shown on map above (the block).

[transfer reader]

1 minute ago, Davefevs said:

Defender makes a great block on six-yard line from JWP chance with keeper beaten, rebound falls to JWP for open goal on the angle. Icon 3 isn’t shown on map above (the block).

Block or parried back to him were what I was thinking

Top 5 chances on in that image are ones I think most would call a good chance (or better) when watching a game and without seeing the xG

Does show as someone else said how much we overestimate the ease of scoring goals.

[BigTone]

43 minutes ago, MarcusX said:

Some people have done a really good job here of explaining how it works, why it’s useful and what you can (and can’t) take from it

Its a bit rude for others to just dismiss it as bollocks, likely because they either don’t understand or just because it doesn’t match what they think they’ve seen.

@IAmNickexplained it really well with the comparison to the thoughts we have. Our thoughts are impacted by bias though.

Its probably an age thing for some of us

[Ian M]

1 hour ago, Alessandro said:

Really surprised by those stats (an open goal at 12 yards and a free header at 5 yards) but there we go, who am I to argue with the computers!! 

And yet Williams and Knight ably demonstrated that these chances are often missed.

[Alessandro]

2 hours ago, Ian M said:

And yet Williams and Knight ably demonstrated that these chances are often missed.

Wasn’t so much that they were missed by them, but I’m interested to see what the stats say about the chances of them not being missed, if you know what I mean! All fascinating stuff. 

[The Swan and Cemetery]

16 hours ago, Davefevs said:

….and that is why for ages I’ve been trying to say to you it’s not good for judging the result of a match, and why xg tables based on individual games are pretty futile.  But it is useful for individual player scouting for example.

Worth you looking at Statsbomb’s xG it is far more sophisticated than any others and solved many of the probs of previous models, inc defenders and goalkeeper positions.

Potentially interesting for some in game assessments (accepting that the data for individual xG incidents won’t be perfect)? Eg in @And Its Smith’s goal mouth scramble example, if all 3 had an individual xG of 0.2, that’s a 0.8^3 chance of not scoring which is still over 50%, despite 3 chances that supporters would probably perceive at gilt edged? 

xG strikes me at the type of tool that [insert name of old school manager] would reject completely in favour of “my own eyes” (and half time cups of tea), NP would see as another way of triangulating what’s going on and LJ would rely on entirely (probably sacked by Hibs for demanding their board push the SPL to given up on points based on wins, draws and losses and just rank based on xG). 

Depending on data efficacy xG will be useful for assessing striker performance vs those creating chances for them, etc etc. Are strikers terrible vs not getting enough chances (accepting might because they’re not making the right runs etc - so can only ever be one perspective, not the only data point used)?

[David Brent]

It’s just a bit of a fad. I’m a big fan of analysis but this just feels like squeezing another metric in.

We coped fine without it and we’ll still be here when it’s out of fashion. 

[downendcity]

American football seems obsessed with data, with stats for every conceivable aspect of the game.

In view of that, I wonder whether American owners of English "soccer" clubs promote the increased use of analytical data with their coaching staff and in decision making around player acquisitions and team selection?

[Davefevs]

1 hour ago, The Swan and Cemetery said:

Potentially interesting for some in game assessments (accepting that the data for individual xG incidents won’t be perfect)? Eg in @And Its Smith’s goal mouth scramble example, if all 3 had an individual xG of 0.2, that’s a 0.8^3 chance of not scoring which is still over 50%, despite 3 chances that supporters would probably perceive at gilt edged? 

xG strikes me at the type of tool that [insert name of old school manager] would reject completely in favour of “my own eyes” (and half time cups of tea), NP would see as another way of triangulating what’s going on and LJ would rely on entirely (probably sacked by Hibs for demanding their board push the SPL to given up on points based on wins, draws and losses and just rank based on xG). 

Depending on data efficacy xG will be useful for assessing striker performance vs those creating chances for them, etc etc. Are strikers terrible vs not getting enough chances (accepting might because they’re not making the right runs etc - so can only ever be one perspective, not the only data point used)?

Really worth watching this video.

https://statsbomb.com/news/statsbomb-data-launch-beyond-naive-xg/
 

The goalmouth scramble scenario is exactly why I would never use to create xG results based league tables.  XG gives you an indication of quality of chances created.  I like looking at shot / xG timelines, ie. did we create our chances regularly throughout the game or in batches, how does that compare to any dominance we had, or were they breakaways, etc, etc.. for me it’s just trying to get some metrics to back up what I watched.  And I don’t look just at xG.  I’ll look at all manner of stuff, PPDA (and indicator or pressing), where we regained possession, picked up loose balls, etc.

excuse the crap rendering of the pic above.  It’s PPDA.  It shows how our pressing went down when we equalised.  First time this season thats happened, a drop off.  You could of course say that Hull took the sting out if our comeback.

They’d just made subs a minute before we scored.  Haha (Nelson Muntz voice) was my first thought when Nahki scored, but that energy up top, might’ve ultimately saved them from allowing us to keep in the ascendency.  Perhaps Nige should’ve used his subs straightaway…although that’s hindsight from me.  When we did make subs, we got back at them.

It matters not that “we could all see it with our own eyes”, because sometimes we miss stuff.  Data helps up confirm what we see, sometimes it highlights things we’ve missed.

Not having a go at Toby on RTV but he said we dominated the game, and was surprised by the possession stats.  I thought he was incorrect on both dominance and possession.  The data confirmed it.

1 hour ago, David Brent said:

It’s just a bit of a fad. I’m a big fan of analysis but this just feels like squeezing another metric in.

We coped fine without it and we’ll still be here when it’s out of fashion. 

It’s not a bit of a fad, it’s evolving every season, it’s getting used more and more, now in mainstream.  It might go out of fashion as something better comes in.

Its not changing the underlying game one little bit, nor is it trying to, but what it is doing is improving analysis of the game.

What did you think when you first saw possession stats in a game?

[ExiledAjax]

2 hours ago, David Brent said:

It’s just a bit of a fad. I’m a big fan of analysis but this just feels like squeezing another metric in.

We coped fine without it and we’ll still be here when it’s out of fashion. 

A fad that's already been around for 8 years and which every major betting company, media company, and football club uses in some manner or other to make a bunch of decisions and cash.