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Alisson Wonderland

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Oncy said:
I notice ILD has just gone ahead and stolen this thread title for his Fantasy Football team.
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Yeah, busted. I always use Obi Wan Kenobi Nil but decided to mix it up.

On side note, does anyone keep scrolling when xG or other alphabet stats are being discussed?
 
Atlas said:
I rarely actually feel old. plus LTW was on it right away
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Yah ... in hindsight, it was a mistake ... not because i don't love the little rascals (despite the white hairs on my beard and lack of hair on my head they've caused) - but it would have been nice to travel with my wife a bit by our own ... You know, explore the world a little
 
Rosco said:
You've managed to agree with me on the limits of xG, it takes into account whether a shot from a certain position is saved or not, and noted some of the factors not measured in xG which do impact on whether a shot is saved.

So how do you come to the conclusion that other factors won't be an issue ?

Did you just accidentally understand xG for a second ?

He'll face a better quality of opposition week to week than he did last season. He's now playing in a team that doesn't give up many shots, but tends to give away high quality chances.

They will undoubtedly be a factor. He could be the exact same goalkeeper next season and his xG could drop significantly. It's only when you have a number of years of data that you can make a judgment based on xG. One season is virtually meaningless. The second season can give you a steer on how real the first years stats were and so on.

The notion that it could only be his fitness or some personal issue that will affect xG is just nonsense.
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Whilst querying whether I 'accidentally' understand xG it seems you still do not since you are mentioning 'quality of teams' & 'high quality chances' etc. xG for a keeper is a pretty damn simple algorithm that doesn't require those additional parameters and neither should it ... the ball is coming from this position, from that distance, at this speed and going into that area of the goal ... what are the odds of the keeper saving it.

I agree one season is not definitive, but hardly meaningless because the keeper still made a higher or lower number of saves than expected so may be indicative of long term expectations. Though that said any keeper can have a good/bad season in regard to saves, they simply don't make enough in one season to be statistically viable proof.
 
As soon as I see "xG" my brain automatically switches off. I can't help it.
 
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Frogfish said:
Whilst querying whether I 'accidentally' understand xG it seems you still do not since you are mentioning 'quality of teams' & 'high quality chances' etc. xG for a keeper is a pretty damn simple algorithm that doesn't require those additional parameters and neither should it ... the ball is coming from this position, from that distance, at this speed and going into that area of the goal ... what are the odds of the keeper saving it.

I agree one season is not definitive, but hardly meaningless because the keeper still made a higher or lower number of saves than expected so may be indicative of long term expectations. Though that said any keeper can have a good/bad season in regard to saves, they simply don't make enough in one season to be statistically viable proof.
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so you don't understand it.

thanks.
 
Why can't we all just agree that XG is a retarded Twitter statistic that noone other than Sky Sports Fucktards actually cares about ?
 
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Frogfish said:
It's actually hilarious you think you do.
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We've done this dance before, and you never come out well for it

I completely understand the limits of it. You think its some sort of pure statistic that evaluates goalkeepers. It doesn't because it lacks sufficient context (for example, one thing which will impact shot quality is how close defender is to the shooter - that isn't captured in the metric and has a huge influence on shot quality) , and that's why there will be a variability in it for the vast majority of keepers - making it unreliable as a ground upon which to judge a keeper, especially with one season of data.
 
Rosco said:
We've done this dance before, and you never come out well for it

I completely understand the limits of it. You think its some sort of pure statistic that evaluates goalkeepers. It doesn't because it lacks sufficient context (for example, one thing which will impact shot quality is how close defender is to the shooter - that isn't captured in the metric and has a huge influence on shot quality) , and that's why there will be a variability in it for the vast majority of keepers - making it unreliable as a ground upon which to judge a keeper, especially with one season of data.
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And did I claim it was a good metric on which to judge a keeper ? No, in fact I didn't claim anything at all .... so don't tell me what I think because as usual you are so far up your own arse you can only see shit. I simply corrected the misinformation you were spreading and that is what you have taken objection to, you simply hate being contradicted in any way. You do know that xG is re-assessed by division too don't you ? No ? Well that explains a lot re. your 'quality of teams' comment .... 🙄
 
Christ on a fucking bike!
Can we just let that motherfucker stand in goal and get shots to the face before we judge him?!
 
Dirty Sanchez said:
@Rosco doesn’t understand it either. Please explain it us again.

Especially the part about keepers tendency to regress to the mean.
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I'll tell you what, I'll quote from people who say it in a way you might understand it.

For example Bobby Gardiner on the Ringer:
'In the same way that most goal scorers’ shot conversion fluctuates from season to season, goalkeeper shot-stopping is notoriously prone to regressing to average conversion. Nonetheless, there are elite players who manage to over-achieve for extended periods, and these particularly talented shot-stopping goalkeepers tend to show up after a couple of seasons of data.'

Or from Statsbomb:
https://statsbomb.com/2014/05/are-some-goalkeepers-better-at-saving-shots-than-others/

The key point in this analysis is not to measure the shot stopping performance of any goalkeeper, but to instead look at how repeatable the shot stopping performances are from one period to another. After all if they aren’t repeatable, be that due to variance, luck or something else we aren’t currently measuring, decisions and actions taken by teams shouldn’t be the same as those that they would take if they were known to be repeatable. Isn’t that right football industry?

A startling finding in that article is that:
'Even when we use the advanced ExpG2 metric to assess how well a goalkeeper performed over a series of 100 on target shots we can still only expect it to explain just 5% of their performance over the next 100 on target shots he faces.

As an average goalkeeper faces approximately 4 on target shots per game this means we need to assess a keeper over about 25 games to only get a 5% steer towards how he will perform over the next 25 games. Pause and think of the implications of that.'

The next part is particularly interesting, and the reason why I say any justification for signing Alisson thay relies on xG or any other stat is misguided at best:

Of course there are goalkeepers that save shots better than others. But for every goalkeeper such as David de Gea that have consistently over performed (1.23 and 1.21 is the ExpG2 Ratio for his two sets of 250 shots) we have a Stephane Ruffier who notched up ExpG2 ratios of 1.15 and 0.98 in his two sets of 250 shots. If those two players had been assessed after their first batch of 250 on target shots (which would have taken almost two full seasons to amass) they would both have been assumed to be well above average shot stoppers. However, only one of them went on to repeat it again after they faced another batch of 250 on target shots.

Imagine the analyst that recommended signing Ruffier on the strength of his save performances using an advanced metric over a “large” dataset of 250 shots or 60 games.
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We're making the call on Alisson before he's faced 250 shots on target.

That's a four year old article now. The problems with using expected goals was well known then and even more so now.

Yet we have all the retards on the site quacking on about how it proves Alisson is great.

If he fails to replicate his xG performance those same idiots will be spouting on about its taking him time to settle, there are communication issues and the usual pseudo psychological crap that explain why they were wrong. Instead of actually jist realising the limits of the information they are basing their opinions on.
 
Frogfish said:
And did I claim it was a good metric on which to judge a keeper ? No, in fact I didn't claim anything at all .... so don't tell me what I think because as usual you are so far up your own arse you can only see shit. I simply corrected the misinformation you were spreading and that is what you have taken objection to, you simply hate being contradicted in any way. You do know that xG is re-assessed by division too don't you ? No ? Well that explains a lot re. your 'quality of teams' comment .... 🙄
Click to expand...

keep digging
 
Rosco said:
I'll tell you what, I'll quote from people who say it in a way you might understand it.

For example Bobby Gardiner on the Ringer:
'In the same way that most goal scorers’ shot conversion fluctuates from season to season, goalkeeper shot-stopping is notoriously prone to regressing to average conversion. Nonetheless, there are elite players who manage to over-achieve for extended periods, and these particularly talented shot-stopping goalkeepers tend to show up after a couple of seasons of data.'

Or from Statsbomb:
https://statsbomb.com/2014/05/are-some-goalkeepers-better-at-saving-shots-than-others/

The key point in this analysis is not to measure the shot stopping performance of any goalkeeper, but to instead look at how repeatable the shot stopping performances are from one period to another. After all if they aren’t repeatable, be that due to variance, luck or something else we aren’t currently measuring, decisions and actions taken by teams shouldn’t be the same as those that they would take if they were known to be repeatable. Isn’t that right football industry?

A startling finding in that article is that:
'Even when we use the advanced ExpG2 metric to assess how well a goalkeeper performed over a series of 100 on target shots we can still only expect it to explain just 5% of their performance over the next 100 on target shots he faces.

As an average goalkeeper faces approximately 4 on target shots per game this means we need to assess a keeper over about 25 games to only get a 5% steer towards how he will perform over the next 25 games. Pause and think of the implications of that.'

The next part is particularly interesting, and the reason why I say any justification for signing Alisson thay relies on xG or any other stat is misguided at best:



We're making the call on Alisson before he's faced 250 shots on target.

That's a four year old article now. The problems with using expected goals was well known then and even more so now.

Yet we have all the retards on the site quacking on about how it proves Alisson is great.

If he fails to replicate his xG performance those same idiots will be spouting on about its taking him time to settle, there are communication issues and the usual pseudo psychological crap that explain why they were wrong. Instead of actually jist realising the limits of the information they are basing their opinions on.
Click to expand...
Nope - still not getting it. Can you go back over the part about how much data we really need?
 
The thing is , do we really struggle to evaluate a goalkeeper before the inception of xg ? Hasn't hes shit / he's not shit shit / he's boss always been kinda obvious ?

How does XG even work when a keeper moves teams , let alone leagues ?
 
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