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*******Spurs v PSG*******Official OMT*******

billyiddo said:
If a shot taken has a high xg then surely by definition it is a good chance that has been created? Whether or not the person on the end of the shot has good finishing ability doesn't change that. Agree on the cumulative figures.
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Yes but you find that most people don't talk about the individual shot in terms of xG, they tend to talk about team xG. But I'll admit in the example you gave it's a reasonable description of how often someone would finish a chance taken from that spot.
 
Muttley said:
Here's a question for all you xPerts.

When Spence got to the by-line last night, refused to use his left foot and then got his right foot cross blocked at source what does that do for xG. He could clearly slide it into the 18 yard box with his left if he wasn't being such a numpty. There should have been a chance created.
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The answer is Jane, and she 1.6m from the nearest fire extinguisher.
 
Bishop said:
Yes but you find that most people don't talk about the individual shot in terms of xG, they tend to talk about team xG. But I'll admit in the example you gave it's a reasonable description of how often someone would finish a chance taken from that spot.
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As you mentioned earlier it needs to be viewed alongside no. of shots to have any meaning in that regard
 
Bishop said:
You're mis understanding a pretty important distinction. Every shot is its own event with its own probability:

  • A 0.15 xG chance means:
  • A 0.03 xG shot from 25 yards might look nice in the highlights, but:

This is the problem with looking at xG as a cumulative stat.

But those probabilities aren’t additive events in the real, lived match. They don’t reinforce each other. Each shot is an independent low-probability moment.

If you take 20 shots at 0.10 xG each, you reach something like 2.0 xG.

But what does that really mean?

  • Each of those shots is 90% likely not to be a goal.
  • The match can easily end with 0 or 1 goals, and that’s not surprising.


xG is a per-event probability; total xG is just the sum of many small independent events, not a prediction of the final score.

The way you're thinking of xG you would think a higher number would better when in reality
it just means more summed probability. A team with 1.0 xG from a few big chances can be far more dangerous than a team with 2.0 xG from 25 weak ones. Cumulative xG doesn't tell you anything about the quality of the individual chances.
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xG does make sense cumulatively. If you have 2 shots each with xG 0.5 you may expect 1 goal but of course you could have 0, 1, 2 or even 3 goals if someone wants to score an own goal for you, there is a lot of variation when looking at just 1 game.
Whereas if you have 20 shots each with xG 0.05 you may expect 1 goal but of course you could have 0, 1, 2, 3, 4 or whatever, as sometimes your luck is in and loads of shots go flying in from half way, when looking at just 1 game.



But more importantly, it gains accuracy over longer time periods e.g. 10 games or 40 games or 100 games.
Because one individual match can have massively different outcomes based on the smallest deflection or piece of luck.

For instance look at last year's table and look at the xG and the xGA and the xPts
There is a massive correlation between the actual finishing standings and the xPts
Yes of course there are outliers and variation, but there is a massive correlation

Likewise the year before https://www.xgstat.com/competitions/premier-league/2023-2024/standings

If you did this over 10 years the correlation would get stronger and stronger, so it is not bunkum.
 
Bedfordspurs said:
Well
It’s experts rather than old men
But still using technology
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Not sure, I've seen loads of lads who haven't played in one year i was with the PL making a name for themselves to the detriment to the game on the pitch.

Someone said earlier and there is alot to be said about it.....its an entertainment sport and the eye test is as crucial as anything

Give me someone thay scores and assists as a metric over miles run or any other metric like that.
 
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Bishop said:
You're mis understanding a pretty important distinction. Every shot is its own event with its own probability:

  • A 0.15 xG chance means:
  • A 0.03 xG shot from 25 yards might look nice in the highlights, but:

This is the problem with looking at xG as a cumulative stat.

But those probabilities aren’t additive events in the real, lived match. They don’t reinforce each other. Each shot is an independent low-probability moment.

If you take 20 shots at 0.10 xG each, you reach something like 2.0 xG.

But what does that really mean?

  • Each of those shots is 90% likely not to be a goal.
  • The match can easily end with 0 or 1 goals, and that’s not surprising.


xG is a per-event probability; total xG is just the sum of many small independent events, not a prediction of the final score.

The way you're thinking of xG you would think a higher number would better when in reality
it just means more summed probability. A team with 1.0 xG from a few big chances can be far more dangerous than a team with 2.0 xG from 25 weak ones. Cumulative xG doesn't tell you anything about the quality of the individual chances.
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I think if you have 20 x 0.1 xG chances, the probability of 0 goals is still as low as 12%.

Whereas for 2 x 0.5 xG chances, the probability is 25% - twice as likely.
 
Bishop said:
You're mis understanding a pretty important distinction. Every shot is its own event with its own probability:

  • A 0.15 xG chance means:
  • A 0.03 xG shot from 25 yards might look nice in the highlights, but:

This is the problem with looking at xG as a cumulative stat.

But those probabilities aren’t additive events in the real, lived match. They don’t reinforce each other. Each shot is an independent low-probability moment.

If you take 20 shots at 0.10 xG each, you reach something like 2.0 xG.

But what does that really mean?

  • Each of those shots is 90% likely not to be a goal.
  • The match can easily end with 0 or 1 goals, and that’s not surprising.


xG is a per-event probability; total xG is just the sum of many small independent events, not a prediction of the final score.

The way you're thinking of xG you would think a higher number would better when in reality
it just means more summed probability. A team with 1.0 xG from a few big chances can be far more dangerous than a team with 2.0 xG from 25 weak ones. Cumulative xG doesn't tell you anything about the quality of the individual chances.
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I know full well that each shot is one event with it's probability. And that the total xG is cumulative. I also understand that a higher number in isolation in one game doesn't equal better.

You may very well have an xG of 1 or 2 and score zero goals. Big chances or small chances, we've all seen those games. And that's just how probability and variance works.

For me a higher summed probability is better than a lower summed probability, in isolation. Sure creating big chances is also good, but again with big chances a higher summed probability of those is better than a lower one.

Flip a coin twice, on average you'll get heads once. Two 0.5 xG chances, on average you'll score once.

Roll a 10 sided dice 10 times, on average you'll hit 10 once. 10 0.1 xG chances, on average you'll score once.

It's not a prediction of the final score. Probabilities aren't predictions, they're probabilities. But over enough time a higher probability will lead to a higher number of goals.

The difference between big and smaller chances is relevant, and also included in xG numbers if one wants to Iook at it beyond the cumulative number. If a team consistently creates only low probability chances, but with a fairly high xG that's not going to be great. But it's still better than creating a low number of low probability chances. And the majority of teams aren't as skewed towards low probability chances for that to be super relevant imo.
 
Grays_1890 said:
Not sure, I've seen loads of lads who haven't played in one year i was with the PL making a name for themselves to the detriment to the game on the pitch.

Someone said earlier and there is alot to be said about it.....its an entertainment sport and the eye test is as crucial as anything

Give me someone thay scores and assists as a metric over miles run or any other metric like that.
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Well my nephew is doing his masters
Has done about 8000 hours of doing the analysis stuff so far
And will likely get paid about …. £25k if he gets a job after his stint at derby
If the rules are defined correctly you don’t need to have played
Weirdly derby have asked him to the do the FA scouting course, so they can get him doing some scouting. His scouting would be done the same way before they would send an old man in to verify what he has seen
Daft
 
Bedfordspurs said:
Well my nephew is doing his masters
Has done about 8000 hours of doing the analysis stuff so far
And will likely get paid about …. £25k if he gets a job after his stint at derby
If the rules are defined correctly you don’t need to have played
Weirdly derby have asked him to the do the FA scouting course, so they can get him doing some scouting. His scouting would be done the same way before they would send an old man in to verify what he has seen
Daft
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It must be a lot harder to scout players these days, clubs change managers and systems so often they must spend months looking for x and y and then told to forget it and find a and b.
 
K.D.D.D.D.Soc said:
It must be a lot harder to scout players these days, clubs change managers and systems so often they must spend months looking for x and y and then told to forget it and find a and b.
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I'd have thought a lot of scouting is about building up player knowledge as opposed to purely transfer specific - if you have that, then when you want a specific player you already have base from which to work from
 
K.D.D.D.D.Soc said:
It must be a lot harder to scout players these days, clubs change managers and systems so often they must spend months looking for x and y and then told to forget it and find an and b.
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It’s data and data
Then in effect you select what parameters the manager wants
Obviously there is a lot more to it
 
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