xG Discussion

[urban.spaceman]

Can we give it it's own thread in the Forum Help section so that I never have to read about it?

 

Asking for an extremely selfish friend.

[Fox92]

40 minutes ago, egg_fried_rice said:

Same reason you see stats like shots, tackles, corners, fouls, and bookings. To provide additional context.

I get shots/corners/fouls because it actually happened.

[egg_fried_rice]

5 minutes ago, Fox92 said:

I get shots/corners/fouls because it actually happened.

xG indicates the quality of chance created, for example a one on one has a higher xG than a 30 yard speculative effort. It is completely based on events that actually happened in the game.

Edited 24 October 2019 by egg_fried_rice

[stripeyfox]

9 minutes ago, urban.spaceman said:

Can we give it it's own thread in the Forum Help section so that I never have to read about it?

 

Asking for an extremely selfish friend.

 

Things "new" to football I never want to hear/see/read about:

 

• Expected Goals
• Fans chanting "V.A.R." during a game
• More to follow.....

 

 

[RowlattsFox]

Its a good indicator that a team is not creating too many clear cut chances and will obviously mean more when teams are not getting results. I don't need a shitty over-the-top stat to tell me that though.

[stripeyfox]

1 minute ago, egg_fried_rice said:

xG indicates the quality of chance created, for example a one on one has a higher xG than a 30 yard speculative effort. It is very much based on events that actually happened in the game.

so is it really a way of validating that sometimes a team that doesn't play "better" than their opponents actuallly win a game, or vice versa?

 

 

[Dahnsouff]

2 minutes ago, stripeyfox said:

 

Things "new" to football I never want to hear/see/read about:

 

• Expected Goals
• Fans chanting "V.A.R." during a game
• More to follow.....

 

 

• New White Hart Lane ?

[worth_the_wait]

When you play a team, there's only one stat that matters.   

 

Which team scored the most goals?

 

All the other stats are irrelevant, meaningless sphericals

[urban.spaceman]

7 minutes ago, stripeyfox said:

 

Things "new" to football I never want to hear/see/read about:

 

• Expected Goals
• Fans chanting "V.A.R." during a game
• More to follow.....

 

 

Ugh. Hate that one. 

[RoboFox]

Even Duncan Alexander looks bewildered by his own explanation of xG.

 

[BrummieFOX]

2 minutes ago, worth_the_wait said:

When you play a team, there's only one stat that matters.   

 

Which team scored the most goals?

 

All the other stats are irrelevant, meaningless sphericals

So you genuinely don't think stats can tell us anything about a team, their performance, weaknesses/strengths? 

[Mickyblueeyes]

We’ve played Chelsea, United and Liverpool away. We’ve played a solid Burnley side and a very good Wolves side at home. That’s five games in which creating chances just based on the very nature of the opposition would’ve been hard to come by. Old Trafford is still one of the most daunting and difficult places to go to regardless of the quality of the team. 

 

The stats at this stage mean nothing. The results are good enough to get us third. The latter means more at this stage.

[egg_fried_rice]

12 minutes ago, stripeyfox said:

so is it really a way of validating that sometimes a team that doesn't play "better" than their opponents actuallly win a game, or vice versa?

 

 

Well, it's just a stat. One that can be used for many purposes. But I suppose that's one superficial use, yes.

 

We see it all the time in football - Team A batters Team B creating numerous good chances but can't find the back of the net. They have a high xG. Team B creates nothing other than one decent chance which they stick away. They have a low xG.

 

Ultimately it's the actual goals that count and Team B win. But Team A can look at their high xG to and say they didn't perform badly per se and there were no fundamental underlying issues, their finishing was just poor. Team A played the better football, in part indicated by a higher xG, but still lost the game.

 

8 minutes ago, worth_the_wait said:

When you play a team, there's only one stat that matters.   

 

Which team scored the most goals?

 

All the other stats are irrelevant, meaningless sphericals

Well of course, and no one would debate otherwise. It just provides interesting context for some.

Edited 24 October 2019 by egg_fried_rice

[daventry_fox]

4 minutes ago, BrummieFOX said:

So you genuinely don't think stats can tell us anything about a team, their performance, weaknesses/strengths? 

It can, but it's doesn't really matter at after the final whistle. As the result can no longer change.

 

I always use Spain as the example their passing stats were through the roof both passes made and completed. Then when you actually watched them play you realise just how missleading those stats were. As most of them were 2 yard passes that actually lead to absolutely nothing or even lead to them making any progress up the pitch. 

 

 

[Xen]

54 minutes ago, egg_fried_rice said:

Yes, penalties are the same and are not included in the normal xG stats. Corners will have a statistical number on the likelihood of being scored before they are taken (it's very low iirc), but the xG is taken from where the player meets the ball once it arrives. xG is judged from where and when the shot is taken.

To give an example of this, Vardy had a clear-cut chance early in the season (I think against Chelsea) where Perez crossed it in and if he'd made any contact with it whatsoever it probably would've gone in (so xG would've been about +0.9 from that chance alone). However, he didn't reach the ball, so the xG was a flat zero.

[daventry_fox]

32 minutes ago, Cujek said:

its a load of bollocks.

 

 

I agree, Its just a fad. You don't need statistical data to know whether player X should have scored a certain chance or not

 

And I don't know about anybody else but I certainly don't need statistical data to tell me not to scream shooooot at Johnny Evans when he's 30 yards out with the ball

[st albans fox]

8 minutes ago, Mickyblueeyes said:

We’ve played Chelsea, United and Liverpool away. We’ve played a solid Burnley side and a very good Wolves side at home. That’s five games in which creating chances just based on the very nature of the opposition would’ve been hard to come by. Old Trafford is still one of the most daunting and difficult places to go to regardless of the quality of the team. 

 

The stats at this stage mean nothing. The results are good enough to get us third. The latter means more at this stage.

Exactly mickey 

 

Xg is a very useful stat - a club that is underperforming wrt xg is in need of a finisher. a club which isn't creating enough good opportunities is probably not going to invest in a finisher.  if you outperform your xg over a season then you should worry a bit because you surely cannot continue to be over clinical

 

9 games is way too early to be taking too much from these stats as mickey explains above 

[HighPeakFox]

Ee heck. 

[messerschmitt]

3 minutes ago, Xen said:

To give an example of this, Vardy had a clear-cut chance early in the season (I think against Chelsea) where Perez crossed it in and if he'd made any contact with it whatsoever it probably would've gone in (so xG would've been about +0.9 from that chance alone). However, he didn't reach the ball, so the xG was a flat zero.

This is one one the things that I was unsure about and surely this distorts the figures, if a player gets the ball 40 yards out runs towards the goal and rounds the keeper before being tackled, that Xg is zero but if he shot from 40 yards when he got it the XG would be higher, you would think running towards the goal and rounding the keeper would give you a better chance of scoring than the shot but XG doesn't see it like that?

[egg_fried_rice]

Just now, messerschmitt said:

This is one one the things that I was unsure about and surely this distorts the figures, if a player gets the ball 40 yards out runs towards the goal and rounds the keeper before being tackled, that Xg is zero but if he shot from 40 yards when he got it the XG would be higher, you would think running towards the goal and rounding the keeper would give you a better chance of scoring than the shot but XG doesn't see it like that?

it doesn't distort the figure, it's just something that xG doesn't measure.

 

You could look at dribbles attempted, successful take ons and take those figures into account too.

 

Fwiw, a shot from 40 yards would have a very low xG. And to play devil's advocate - if in your first example the striker never even took a shot before he was tackled, how can he have any chance of scoring at all? In essence, what he was doing was attempting to turn a low xG chance into a higher xG chance, but was unsuccessful in doing so.

 

xG is not the perfect stat designed to be used in isolation as a catch all for a team's total quality. It simply tells you the number of goals you should expect to score from the shots you did take and shouldn't be treated as anything more or less than that.

[messerschmitt]

After the Burnley game on Saturday I was amazed to see that they had a better XG than we did, having now watched the game twice I still don't see this. When Vardy headed the ball this must have had a higher XG than when Wood scored, he had to jump between two defenders and only had the near corner to put it, even then Kasper got a hand on it? The only other decent chance they had was at the beginning of the second half when Wood turned on a dropping ball and put it wide.

[StriderHiryu]

10 minutes ago, st albans fox said:

 

Xg is a very useful stat - a club that is underperforming wrt xg is in need of a finisher. a club which isn't creating enough good opportunities is probably not going to invest in a finisher.  if you outperform your xg over a season then you should worry a bit because you surely cannot continue to be over clinical

 

That's a meaningful example of where the xG stat can be used in football. If you've read the 5000-1 book by Jonathan Norwood it gives a bit more insight, but our scouting team had developed a series of scouting models, using certain stats that they identified in "undervalued" players who after watching them live they would potentially sign. Huth had a high aerial clearance rate, Albrighton had a high chances created rate from his early crosses, Kante had insane tackling stats, etc. Liverpool also have their own model and this has led to them finding players like Salah, Gomez and Robertson and it's working for them. 

 

That said the xG stat specifically does confuse me. As @messerschmitt points out, Burnley had a higher xG in our game against them, but that didn't feel indicative of the game at all. It's not the first time I've seen such an occurrence, though at the same time it's been shown that over a course of the season it's quite reflective of a team's performance. 

 

Perhaps though our xG rate is one of the reasons why that piece in the Telegraph about wingers appeared. Those are the sort of players who should be boosting that rate for any team and all of Barnes, Albrighton, Gray and Perez have been average at best so far. 

[messerschmitt]

Yeah, thanks I see what your saying, it did make me think that if your XG was less than the opponent you didn't deserve to win the game or were lucky. Like you say XG doesn't  take account of intent to make the XG of a chance larger and losing it. In the first half a Burnley player had what I think was a shot, it was blocked and took at least 2 deflections off Leicester players before falling to Chris Wood who tried to slide it under Kasper. I guess this would count as two XGs in one attack, where as in the second half we had a good passing movement where eventually Ricardo ended up in the six yard box and tried a pass where we had two players at the far post who would have had a tap in but the pass was blocked so no XG.

[KingsX]

19 hours ago, Foxymcoxy said:

Can somebody tell me the formula which calculates xG? I'm particularly interested in the variables contributing to the "quality of chance" and how they are modelled? If you can't answer questions like this you can't say the stat is good because you're guessing.

 

That is entirely untrue.  Most (all?) of the models are proprietary.  The events are recorded, and numbers calculated, by companies that sell the results (or by clubs themselves, at our level).  We are simply accessing what end results get published on the Web.

 

Read this carefully.  There will be a quiz:

 

The simple model looks at each attempt (not just on goal) and assigns an Expected Goals figure.  e.g. a shot from that location has proven to result in a goal 25% of the time.  So 0.25 xG.  This may be adjusted for other factors which are trade secrets, e.g. whether there is a defender between the shot and the frame, and/or the historical success rate of the player taking the action.  (So in more advanced models, a Vardy shot would have a higher xG than the same Ndidi shot.)

 

There are non-shot models that estimate how many goals a team “should” have scored based on passes, interceptions, take-ons and tackles around the opposing team’s goal.  e.g. intercepting the ball at the opposing team’s penalty spot results in a goal about 9 percent of the time (0.09 xG), and a completed pass received at the center of the six-yard box leads to a goal about 14 percent of the time (0.14 xG).

 

I’d bet the house that clubs buying and using these stats, use a combination of approaches, plus advanced stats that do require a PhD.  But they are not about to give me a peek behind the curtain.

 

Some of you would fire our new analytics whiz as fast as Ranieri fired the sports psychologist.  Maybe the same ones who would rather see us back in the Championship playing real blood-and-guts football?  You would get your wish, briefly, on our way to League Two.

 

Edited 24 October 2019 by KingsX

[Foxxed]

I want to know how Christian Fuch's throw in count towards xG.

 

2 hours ago, Dahnsouff said:

 

For each scoring opporunity in the game

- Given the position from it was taken

 

Touchline

 

2 hours ago, Dahnsouff said:

- The type of action (shot, header)

 

Ball thrown

 

2 hours ago, Dahnsouff said:

- The nature of how the ball was received

 

With surprise

 

2 hours ago, Dahnsouff said:

- Proximity of opposition players

 

Nearby

 

2 hours ago, Dahnsouff said:

 

You can gauge how historically likely are you to score

 

 

 

 

 

It's a load of old geezers going "Oooh I reckon they should've scored there" and "their attackers aren't getting in good positions" but using numbers instead isn't it.