Author Topic: Using Stats to Talk about Liverpool  (Read 137878 times)

Online spider-neil

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Re: Using Stats to Talk about Liverpool
« Reply #1080 on: February 22, 2019, 09:11:41 AM »
Collating attacking stats is relatively easy.
You have the 'hockey assist', the pass before the pass that leads to a goal.
You have the 'assist' the pass before the goal.
The goal itself.
The difficulty of the chance (xG)

Working up defensive stats is much harder.
You have aerial deals, inceptions, blocks, tackles. But it's very black and white. And in my humble opinion isn't creating a clear picture of what is happening in defense. Because the defense has to work as a unit where it needs to take in several players, not just one. What if a defender is brilliant at positioning, therefore, make very little tackles? What if one defender is so brilliant at headers that opposition hand on the less capable header of the ball? Collecting defensive stats seems far more open to interpretation and nebulous.

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Re: Using Stats to Talk about Liverpool
« Reply #1081 on: February 22, 2019, 10:06:59 AM »
Collating attacking stats is relatively easy.
You have the 'hockey assist', the pass before the pass that leads to a goal.
You have the 'assist' the pass before the goal.
The goal itself.
The difficulty of the chance (xG)

Working up defensive stats is much harder.
You have aerial deals, inceptions, blocks, tackles. But it's very black and white. And in my humble opinion isn't creating a clear picture of what is happening in defense. Because the defense has to work as a unit where it needs to take in several players, not just one. What if a defender is brilliant at positioning, therefore, make very little tackles? What if one defender is so brilliant at headers that opposition hand on the less capable header of the ball? Collecting defensive stats seems far more open to interpretation and nebulous.
Theres a link from one of our data scientists public stuff that has a model that covers this sort of thing in terms of defending space, I'll try find it


Found it
https://twitter.com/the_spearman/status/966750560530595843?s=19
« Last Edit: February 22, 2019, 10:10:18 AM by Chris~ »

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Re: Using Stats to Talk about Liverpool
« Reply #1082 on: February 22, 2019, 12:03:19 PM »
Theres a link from one of our data scientists public stuff that has a model that covers this sort of thing in terms of defending space, I'll try find it


Found it
https://twitter.com/the_spearman/status/966750560530595843?s=19

Thanks :)
That is a seriously complex model. It's a pity they can't simplify it and make it available like Opta and Understat.
« Last Edit: February 22, 2019, 12:06:05 PM by spider-neil »

Offline BassTunedToRed

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Re: Using Stats to Talk about Liverpool
« Reply #1083 on: February 22, 2019, 01:03:30 PM »
Thanks :)
That is a seriously complex model. It's a pity they can't simplify it and make it available like Opta and Understat.

He works for Liverpool, so that won't be being made available in any form!

Offline BrandoLFC

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Re: Using Stats to Talk about Liverpool
« Reply #1084 on: March 11, 2019, 05:29:25 PM »
Would this be we haven't improved or would this be we hit this form last year and just kept it going?


Offline JCB

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Re: Using Stats to Talk about Liverpool
« Reply #1085 on: March 12, 2019, 05:19:46 PM »
Would this be we haven't improved or would this be we hit this form last year and just kept it going?


Depends if you're a glass half full or half empty person... ;)

It's also worth noting however that by looking at xGD only you'e unable to see the effects/changes of defence and Attack. So if you have a team scoring shitloads but conceding shitloads who then transition into a team that score less and concede less, the GD (and xgD) won't change too much.

I like to look at the individual components and get an overall picture. Here's Liverpool's data over the same time period and with the same 10 game Moving Average, however the xG data is from Understats so it differs especially as the xGD excludes penalties




Offline ElstonGunn

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Re: Using Stats to Talk about Liverpool
« Reply #1086 on: March 12, 2019, 06:43:13 PM »
Would this be we haven't improved or would this be we hit this form last year and just kept it going?


A bit of that, a bit of Phil in the first half/AOC in the second being fucking incredible last year and not really replacing their contribution (while overall maintaining the same level), and a LOT of Alisson being a gigantic upgrade at keeper, something not captured in those numbers.

Offline BrandoLFC

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Re: Using Stats to Talk about Liverpool
« Reply #1087 on: March 12, 2019, 07:13:45 PM »
I'm not arguing one way or another.  Just think it's an interesting discussion in that everybody has their own definition of "improvement" or lack thereof.  I'm sure there will be people out there that will argue we haven't improved if we don't win the league or CL either in good faith or not.

Offline Yiannis

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Re: Using Stats to Talk about Liverpool
« Reply #1088 on: March 14, 2019, 01:38:52 PM »


Messi in fact doesn't have a recognizable trait.

Offline a treeless whopper

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Re: Using Stats to Talk about Liverpool
« Reply #1089 on: May 23, 2019, 06:13:36 AM »
Do people actually eat beef for Breakfast? Must be some sort of brain food.

Online royhendo

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Re: Using Stats to Talk about Liverpool
« Reply #1090 on: May 23, 2019, 09:04:12 AM »
Split the article off into a separate thread as requested dudes and dudettes. Killer, if your beef post was for that thread, I can only apologise for my oversight. :)
Thoroughly mediocre player.

Regrettably not seen anything in him. Neither for us nor from watching lots of youtube videos after a few on here said he looked good.

Offline farawayred

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Re: Using Stats to Talk about Liverpool
« Reply #1091 on: July 30, 2019, 08:45:45 PM »
That's not quite along the same path this thread has followed, but I'll put his here anyway. Mods, feel free to delete.

I think this is an interesting thread with just about enough material to apply the "wisdom of the crowd" statistical theory. The idea is that a crowd can predict more accurately an average number then an individual person. Try this with a crowd trying to guess how many marbles are in a jar, and given enough numbers, you'd get <5% error.

So, I got bored at work and started counting... Funnily, this thread has a lot of posts in the June 2-7 time frame, and yesterday and today, but nothing in between. So are we going to win the league?

I separated the answers into (1) win the league, (2) some second, and (3) top four, meaning 3rd or 4rt place. I took only the specific answers, and omitted "we will win a double", which does not necessarily include the league. In the event that someone predicted 2nd or 3rd, I put 0.5 weight in (2) and 0.5 weight in (3). here are the results:
Win     2nd     3/4
27        1         0           Results from June 2-7 only
8.5       8       10.5        Results from July 29-30 (5 people had 2nd or 3rd answer, one said the title is between us and City)

Now, these are small statistics, but they are speaking volumes! In the beginning of the summer, the crowd (we, the fans) thought that we will win the league. At the end of July, a week before the transfer window close, the crowd concludes that we will finish most likely 2nd. That's how much the opinion changed, even though only one person (PoP) specifically expressed this.

Food for thought.
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Offline demain

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Re: Using Stats to Talk about Liverpool
« Reply #1092 on: December 28, 2019, 11:36:13 AM »
Been bugging me slightly for a while but most xG models that I have seen have Liverpool in second place behind City, which is obviously something riling Guardiola as well.

I am biased so I am not willing to accept that Liverpool have been lucky this season, nor have I ever thought that xG models were robust enough to pass off as anything more than entertainment draped in dumbed down statistical sophistication for football audiences, given that the definition of a chance is highly subjective.

There have been more than a few occasions this year when I have thought that there is something drastically wrong with how the data is being presented, or is it just that I am too biased to think rationally?

Glad to hear what those that work with football statistics have to say about it.
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Offline groove

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Re: Using Stats to Talk about Liverpool
« Reply #1093 on: December 28, 2019, 11:50:19 AM »
Yeah, we've been lucky and people tend to drastically underestimate the hidden chance in pretty much everything, never mind football. But who cares? It's been 30 years. I personally don't give a shit, because I accept there's huge amounts of luck that go into where a team finishes each season anyway and I feel in the past we've been on the end of plenty of bad runs of luck.

You kinda answered your own question by the way. If you're going to be biased (which is fine) then why even look at any statistical stuff?

Offline BassTunedToRed

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Re: Using Stats to Talk about Liverpool
« Reply #1094 on: December 28, 2019, 12:12:28 PM »
I don't think Liverpool have been particularly lucky - if you look at the data from Five Thirty Eight, and award an xG win to whichever side leads by at least 0.5 xG, you find Liverpool have won six more points than their performances have theoretically deserved. By this measure, the matches with Southampton, Chelsea, Man United and Man City should've been draws, but three of them were won. A touch lucky perhaps? But hardly daylight robbery.

But it is also fair to say City have been unlucky, as the attached table will show. As a couple of extreme examples, Spurs only had three shots but got a draw, and Newcastle only had six (five from outside the box) and got a point too. But xG can hide game state issues too - based on the xG totals they deserved to beat Norwich and United, but they were two goals down in those games, which is very tough to come back from (unless you're Wolves  ;)). Their win over Chelsea should've been a draw too, it hasn't all gone against them.

In terms of how the data is being presented, I guess it depends where you're looking and how they calculate it. It's only ever a guide.
« Last Edit: December 28, 2019, 12:14:31 PM by BassTunedToRed »

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Re: Using Stats to Talk about Liverpool
« Reply #1095 on: December 28, 2019, 12:14:10 PM »
Been bugging me slightly for a while but most xG models that I have seen have Liverpool in second place behind City, which is obviously something riling Guardiola as well.

I am biased so I am not willing to accept that Liverpool have been lucky this season, nor have I ever thought that xG models were robust enough to pass off as anything more than entertainment draped in dumbed down statistical sophistication for football audiences, given that the definition of a chance is highly subjective.

There have been more than a few occasions this year when I have thought that there is something drastically wrong with how the data is being presented, or is it just that I am too biased to think rationally?

Glad to hear what those that work with football statistics have to say about it.
I think the xg models are fine. We did go through a period where we weren't racking up high quality chances like city can after going ahead and were happy to sit on leads after scoring some lower quality chances, or on a 1/2goal lead. Chelsea were a bit like this when they won under Conte. Like anything if you just look at numbers and take them at face value there will be some issues. Like United having a high xg because they had loads of penalties at one point. Or city have a low xg against but per shot the xg is quite high so are more likely to concede more than their xg against.

Offline smithng

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Re: Using Stats to Talk about Liverpool
« Reply #1096 on: December 31, 2019, 05:44:17 PM »
The Royal Institute Christmas Lectures 2019 (on BBC iPlayer) - Secrets and Lies first episode - had one of Liverpoolís backroom boffins on - Tim Waskett (from 28 mins) talking about the data used to analyse football.

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Re: Using Stats to Talk about Liverpool
« Reply #1097 on: January 2, 2020, 12:09:58 PM »
The Royal Institute Christmas Lectures 2019 (on BBC iPlayer) - Secrets and Lies first episode - had one of Liverpoolís backroom boffins on - Tim Waskett (from 28 mins) talking about the data used to analyse football.

Hereís an article about what he said ...

https://trainingground.guru/articles/tim-waskett-the-maths-behind-liverpools-title-charge

Offline BassTunedToRed

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Re: Using Stats to Talk about Liverpool
« Reply #1098 on: January 2, 2020, 02:21:09 PM »
The Royal Institute Christmas Lectures 2019 (on BBC iPlayer) - Secrets and Lies first episode - had one of Liverpoolís backroom boffins on - Tim Waskett (from 28 mins) talking about the data used to analyse football.

Thanks for sharing that, much appreciated.

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Re: Using Stats to Talk about Liverpool
« Reply #1099 on: January 2, 2020, 02:30:10 PM »
Been bugging me slightly for a while but most xG models that I have seen have Liverpool in second place behind City, which is obviously something riling Guardiola as well.

I am biased so I am not willing to accept that Liverpool have been lucky this season, nor have I ever thought that xG models were robust enough to pass off as anything more than entertainment draped in dumbed down statistical sophistication for football audiences, given that the definition of a chance is highly subjective.

There have been more than a few occasions this year when I have thought that there is something drastically wrong with how the data is being presented, or is it just that I am too biased to think rationally?

Glad to hear what those that work with football statistics have to say about it.
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Offline thaddeus

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Re: Using Stats to Talk about Liverpool
« Reply #1100 on: January 2, 2020, 03:18:29 PM »
Been bugging me slightly for a while but most xG models that I have seen have Liverpool in second place behind City, which is obviously something riling Guardiola as well.

I am biased so I am not willing to accept that Liverpool have been lucky this season, nor have I ever thought that xG models were robust enough to pass off as anything more than entertainment draped in dumbed down statistical sophistication for football audiences, given that the definition of a chance is highly subjective.

There have been more than a few occasions this year when I have thought that there is something drastically wrong with how the data is being presented, or is it just that I am too biased to think rationally?

Glad to hear what those that work with football statistics have to say about it.
(all data from https://understat.com/league/EPL)

Our xG differences in isolation aren't huge.  We've scored 7 more than expected - the main beneficiary being VVD who has scored 3 but would have only been expected to score 0.59 - and conceded 3 less than expected.  Leicester and Southampton have the highest swings with +18 and -13(/14) respectively.

The only games where we've had a lower xG than our opponents are:
- Southampton (A).  Won 2-1 but would have expected to lose 2-1.  Southampton have a net -13/14 xG across the season so that's just in keeping with their general performance at both ends of the pitch.
- Chelsea (A).  Won 2-1 but would have expected a 1-1 draw.  Chelsea have a net -8/9 xG across the season so likewise.
- Man City (H).  Won 3-1 but would have expected a 1-1 draw.  Fabinho scored a wonder goal - it happens from time to time - while half their xG came from Kyle Walker's missed header very late on in the game.
(https://understat.com/team/Liverpool/2019)

It should also be noted we had a higher xG than Man U in the only game we dropped any points.  Ignoring that game though the above three results would have cost us 7 points and taken us from 55 points to 48 points.  Even had we lost them it would still be 46 points.

Where it gets screwy - more-so than xG already is anyway - is when that's extrapolated to xPTS (expected points).  The league table has us on an xPTS of 39.49.  That's 15.51 points less than we actually have even though we've only had those three games where we didn't have a higher xG than our opponents and also drew a game where we did have a higher xG!  It just seems the model doesn't cope well when a team does enough to win without running rampant.



If you want to cut through everything though and see how flawed xG is then consider the Son goal against Burnley, the one where he picked up the ball on the edge of his area and ran through the Burnley team before slotting past Nick Pope.  The definition of a wonder goal and not one I can remember anything remotely similar to (George Weah for AC Milan, maybe).  xG has that as a 55% chance of resulting in a goal (a penalty is only 76%!) because of where and how the final shot was executed.

Offline vagabond

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Re: Using Stats to Talk about Liverpool
« Reply #1101 on: January 2, 2020, 03:25:24 PM »
Yeah xG is not a perfect measure by any means. Just consider a situation where a ball is played across the box and a player is inches away from getting a touch for what would be a near certain goal. But because no shot actually happened, that chance won't be included on the xG stats.
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Offline JackWard33

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Re: Using Stats to Talk about Liverpool
« Reply #1102 on: January 2, 2020, 03:32:37 PM »
Yeah xG is not a perfect measure by any means. Just consider a situation where a ball is played across the box and a player is inches away from getting a touch for what would be a near certain goal. But because no shot actually happened, that chance won't be included on the xG stats.

But that nets out over time and what xg misses isnít the point.
Shots correlate to results over time  ... Xg - which is shots filtered for locations - correlates better
Itís the most predictive widely available stat we have ... it isnít perfect by any means but xg models are evolving all the time (to include things like level of pressure on a shot, position of keeper etc)
« Last Edit: January 2, 2020, 03:35:50 PM by JackWard33 »

Offline vagabond

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Re: Using Stats to Talk about Liverpool
« Reply #1103 on: January 2, 2020, 03:37:29 PM »
But that nets out over and what xg misses isnít the point.
Shots correlate to results over time  ... Xg - which is shots filtered for locations - correlates better
Itís the most predictive widely available stat we have ... it isnít perfect by any means but xg models are evolving all the time (to include things like level of pressure on a shot, position of keeper etc)


Yeah I agree with all that. Was just pointing some of the imperfections. That chance would however be measured on xgBuildup (I think?) so there are ways to measure it to get a better picture of the state of the game.
The other improvement I'd like to see is xG models that are responsive to game state (perhaps this is already happening?) I feel like our xG is often lower than it could be because we cruise after going a goal up most games unlike City who keep piling up the chances.
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Offline JackWard33

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Re: Using Stats to Talk about Liverpool
« Reply #1104 on: January 2, 2020, 03:38:35 PM »
Oh and expected points is a pretty clumsy and silly way to use expected goals - donít think those league tables that are widely used now are particularly helpful (they donít account for how teams react to game states for example)

You can say that team A is running hot defensively / offensively over a period of time and be reasonably confident itíll revert to the mean but putting that into a league table probably isnít going to get to much thatís helpful

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Re: Using Stats to Talk about Liverpool
« Reply #1105 on: January 11, 2020, 07:30:23 PM »
Best start ever of any team in Europeís top five leagues. The only stat to mention if any has any criticism of this team.

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Re: Using Stats to Talk about Liverpool
« Reply #1106 on: January 11, 2020, 07:33:13 PM »
Best start ever of any team in Europeís top five leagues. The only stat to mention if any has any criticism of this team.
But it's not a perfect start, is it? Means that this stat can be beaten too.

;)
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Re: Using Stats to Talk about Liverpool
« Reply #1107 on: January 11, 2020, 07:34:17 PM »
But it's not a perfect start, is it? Means that this stat can be beaten too.

;)
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Re: Using Stats to Talk about Liverpool
« Reply #1108 on: January 12, 2020, 07:41:11 PM »
The Idea of xG is intentionally ignoring the skills of the remaining few persons: the striker taking the shot and the goalkeeper/defenders still able to interfere. So when, let's say, Andy Carroll and Luis Suarez both have ten attempts summing up to an xG of 3, in reality Suarez might be expected to score 4 and Carroll only to hit 2. This doesn't mean the team having Suarez is more lucky, they just had the better recruiting.
The same applies onthe other end for the keeper and potentially blocking defenders.

Offline groove

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Re: Using Stats to Talk about Liverpool
« Reply #1109 on: January 13, 2020, 11:48:23 AM »
I think the decent xGs model take into account individual finishing and goalkeeping ability. I think Caley's does at least?

And whilst your Carroll/Suarez example would be correct in the models that don't take this into account, the disparity in finishing ability is not as severe as the numbers you've used there. Messi, for example, is the best finisher in the world. He finishes about 25% above xG, which essentially means he has a 25% more chance to score than the average shot taker. In your example, Suarez is scoring 33% more and Carroll scoring 33% less than the average. In reality they both likely fall within the +/-10% range that the vast majority of footballers fall in.
« Last Edit: January 13, 2020, 11:54:50 AM by groove »

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Re: Using Stats to Talk about Liverpool
« Reply #1110 on: January 13, 2020, 12:01:40 PM »
I think the decent xGs model take into account individual finishing and goalkeeping ability. I think Caley's does at least?

And whilst your Carroll/Suarez example would be correct in the models that don't take this into account, the disparity in finishing ability is not as severe as the numbers you've used there. Messi, for example, is the best finisher in the world. He finishes about 25% above xG, which essentially means he has a 25% more chance to score than the average shot taker. In your example, Suarez is scoring 33% more and Carroll scoring 33% less than the average. In reality they both likely fall within the +/-10% range that the vast majority of footballers fall in.

No, Caley's doesn't take into account individual's ability at all. The most that decent models do is consider the position of defenders and goalkeepers facing the shots in addition to the shot location and shot type.

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Re: Using Stats to Talk about Liverpool
« Reply #1111 on: January 13, 2020, 12:19:51 PM »
https://cartilagefreecaptain.sbnation.com/2015/10/19/9295905/premier-league-projections-and-new-expected-goals

Quote
For each of the following I list the "formula" section of the logistic equation. The full logistic equation is then multiplied by the player adjustment, with regression at the ends to prevent shots from registering above 1 or below 0.

So maybe, not goalkeeping ability, but he does appear to take finishing ability into account somewhat.

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Re: Using Stats to Talk about Liverpool
« Reply #1112 on: January 13, 2020, 12:34:28 PM »
Five Thirty Eight claim their xG model does include the finishing ability of the players taking the shots, though I've never seen them share a player breakdown which might prove this.

Offline JC the Messiah

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Re: Using Stats to Talk about Liverpool
« Reply #1113 on: January 13, 2020, 12:43:06 PM »
Five Thirty Eight claim their xG model does include the finishing ability of the players taking the shots, though I've never seen them share a player breakdown which might prove this.

If it does, Lingard's xG numbers are all multiplied by a factor of 0.000001.
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Offline JackWard33

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Re: Using Stats to Talk about Liverpool
« Reply #1114 on: January 13, 2020, 12:45:59 PM »
I think the decent xGs model take into account individual finishing and goalkeeping ability. I think Caley's does at least?

And whilst your Carroll/Suarez example would be correct in the models that don't take this into account, the disparity in finishing ability is not as severe as the numbers you've used there. Messi, for example, is the best finisher in the world. He finishes about 25% above xG, which essentially means he has a 25% more chance to score than the average shot taker. In your example, Suarez is scoring 33% more and Carroll scoring 33% less than the average. In reality they both likely fall within the +/-10% range that the vast majority of footballers fall in.

Yup and the important thing people should realise is that most players - even high profile players - revert to close to xG which is why its expected goals
Finishing ability is the great myth of most non-data driven football analysis ... although I suspect it'll endure as long as football is played

Offline PoetryInMotion

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Re: Using Stats to Talk about Liverpool
« Reply #1115 on: January 13, 2020, 01:49:57 PM »
https://cartilagefreecaptain.sbnation.com/2015/10/19/9295905/premier-league-projections-and-new-expected-goals

So maybe, not goalkeeping ability, but he does appear to take finishing ability into account somewhat.

Okay, I wasn't aware it took finishing skill into account. I thought it was just the position and shot type - foot, header and after a dribble or a through-ball. Anyway, his model doesn't consider the skill (and number) of the defense/goalie as you've mentioned.

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Re: Using Stats to Talk about Liverpool
« Reply #1116 on: January 13, 2020, 02:07:56 PM »
I think the decent xGs model take into account individual finishing and goalkeeping ability. I think Caley's does at least?

And whilst your Carroll/Suarez example would be correct in the models that don't take this into account, the disparity in finishing ability is not as severe as the numbers you've used there. Messi, for example, is the best finisher in the world. He finishes about 25% above xG, which essentially means he has a 25% more chance to score than the average shot taker. In your example, Suarez is scoring 33% more and Carroll scoring 33% less than the average. In reality they both likely fall within the +/-10% range that the vast majority of footballers fall in.

As a kind of irrelevant aside here, Carroll feels like a strange one to pick because I actually think he's a really good finisher? Particularly, obviously, in the air. He's absolutely lethal. And he strikes quite cleanly with his left.

Poor Andy :(

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Re: Using Stats to Talk about Liverpool
« Reply #1117 on: January 13, 2020, 04:33:59 PM »
As a kind of irrelevant aside here, Carroll feels like a strange one to pick because I actually think he's a really good finisher? Particularly, obviously, in the air. He's absolutely lethal. And he strikes quite cleanly with his left.

Poor Andy :(

He's exactly average.
Better looking than Samie.

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Re: Using Stats to Talk about Liverpool
« Reply #1118 on: January 29, 2020, 11:30:41 PM »
Support the team,Trust & Believe.

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Re: Using Stats to Talk about Liverpool
« Reply #1119 on: January 31, 2020, 03:01:51 AM »
Not sure if this has been raised elsewhere - probably has - but StatsBomb, whose analysts think about the game in some really innovative ways, have for the last little while started to publish their data at https://fbref.com/en.

It has a lot of good information - xG, xA and good GK stats, for example, and also some random stuff like nutmegs (did you know Serge Aurier is the second most frequent exponent of the nutmeg this season?), but it doesn't  have quite the full range of back stuff StatsBomb provides to subscribers.

Well worth a look.
« Last Edit: January 31, 2020, 03:04:33 AM by Redcap »