Football statistics/general analysis/philosophicable pontification thread


#163

My conclusion on xG is that it is actually really good for assessing team defensive and offensive overall performance (ie., xG for and xG against)… to me, it isn’t nearly that good at analyzing individuals because so many of the variables that go into it are related to other people, unless we are talking about mazy-run dribbling exploits that lead to a shot after beating 5 people.

For example, if a player happens to get into the box a lot and his teammates find him, he will have xG through the roof. If he then underperforms his xG, or over performs it, how should that be interpreted? On one hand, you might argue that the player is tricky and finding spaces in crowded zones, doing hard work to find himself open enough to receive and shoot, so a lower conversion rate is not punished as much. On the other hand, the player might be considered wasteful if he underperforms the xG.

Probably more importantly, one shot from inside the box close in can contribute a LOT to xG, so those little single events (again, rare event stats) can have massive impact on a player’s single metric for a game and a little less so for a team’s full xG (make of that what you will). Also, it exclusively measures attempts at goal - nothing else… any offensive or defensive contributions that didn’t lead directly to an attempt at goal are not considered.

In general, I think the model is pretty good predictor over time of a team’s performance though - Nice being the obvious anomaly.

One other thing - xG is not a single algorithm or measure - if you look, there are numerous models built around the concept. Some of them correlate well with team goals, others less so.

What I would find very interesting is if they can expand on it to look more at an xG or xD (delta in goals) as models of showing a players’ total contribution. I suppose one could do a crude measure of team effectiveness to when a player is on the pitch and not, but that is harder given the constantly changing conditions around those variables.


#164

I get the way that the value is established for any given single chance, but how is the overall value for the match calculated then?


#165

That’s actually quite a good use for clubs to see how individuals are doing compared to the 'average likelihood of a goal occurring.

Didn’t I see here that we’re using it to analyse our % chance conversion or basing transfers on it?


#166

Well this is where context comes in. When we’re talking about a striker vs. striker comparison xG might have some use, when we’re talking about a forward like Alexis comparison with another then it has a bit less but still some, but needs other statistics involved for something resembling an interesting argument. That’s why there are also stats like x Assists or x Chances Created, because they look at the passes before the final action.

I agree that a delta model showing a player’s total contribution would be interesting…but it’s complicated in football when the crucial events are much fewer (I suppose this statistic works in basketball, as it does, because there are so many pts). I think the most interesting thing I saw on this front was a metric based on game theory designed by a Basque statistician which I remember talking about on the old forum, but honestly I don’t even know where to find that metric now, and not sure how well it holds up 6-7 years later (think it was in 2009 or 2010 he created it). Burgundy might know better on this front, I remember reading an article he posted on something like ‘passing progression’ last season but that was more of a team metric. There’s this metric called ‘Packing’, which shows how many players are eliminated with a certain pass I think, that my Liverpool fan friend–who wants Keita badly given that he ranked best in Europe in this metric haha–referred to.


#167

I haven’t read this but I imagine it’s an accumulation of all the quality of shots that the team had during the game. Hench how on sky they didn’t show round figures. I guess that’s how it can be quite disproportionate, a team may have 20 shots from 30+ yards yet 2 inside the 6 yard box.


#168

I think xG is a solid foundation to build upon - agree it would take a lot of work but I could imagine starting simple with those x Assists or x Chances Created (this is probably better) and the reciprocal (also harder) in terms of denial.

What might always be tough is some of the defensive positioning subtlety, but yeah the avalanche of data is making more possible - just need smart people to unlock it.


#169

Thanks @will24 :+1:


#170

I’m very torn here because I’d love to agree with old man Dan and James and stick it to those young whipper snapper hipsters who think they are so darn cool, but xG is a stat Theo excels in and makes him look good soooo…yay xG


#171

Thats made me chuckle :smile:

Edit: aren’t we like the same age? (35)


#172

34, but I’m a millennial and you are just on the cusp of being a gen x’er


#173

Thats just a fancy way of saying I’m better right? :smiley:


#174

Can someone give me the low down on why these generations have names?


#175

Knockaert was the first identified using a coding systems that evaluated where a player was in his career, whether they were over achieving and had potential to develop further at City.

“Scouts still go and watch players now and file reports and that is still important, but a big area it makes a difference is in the identification of the player in the first place,” explained Mackenzie.

Some targets City have identified they simply haven’t been able to land…

“Another one was Arkadiusz Milik, who we tried to sign twice. The first time when he was playing in Poland aged 18. He was over achieving. We declared an interest and we watched him.


#176

More meaningful than stats like shots on target and possession for me. xG tells us if it was a 1-0 or 2-0 kind of game. Like who actually made the more likely chances over the 90 minutes. It deserves to make it’s way to mainstream football broadcasting.


#177

West Bromwich Albion is the side to have made the highest proportion of their forward pass attempts into the final third in their own half. And, equally, that Arsenal are the side who have the lowest proportion (nearly 38% for West Brom, just under 6% for Arsenal).

Looking at teams’ percentages for attempts on either wing is interesting…

Interestingly, Arsenal is the team with the least wing presence in this measure, with just over 16% of their forward pass attempts into the final third coming from the flanks.


#178

Haven’t read the article but that’s pretty promising/favourable stats, tbh, it feels like we play a lot more pointless longballs and crosses than that would suggest.


#179

16-17 Premier League usage rates, not surprising to see Alexis top for us.

https://drive.google.com/file/d/0B8bPKtREXelXaDhraFNvOW82UjQ/view


#180

https://twitter.com/guba1a/status/904339642920693761


#181

Buenzemísima! Who said he wasn’t a good finisher!

edit: whoops, just realised that anything above 1.0 would mean that he’s finishing above expectations, no? So that wouldn’t make him an especially good finisher (still above OG7 tho :innocent: )

I guess, also, that isn’t a list in order of pure ranking, as it seems like it’s a list where there’s only big names? Surely the Chicharitos and OG12s of the world would figure in there somewhere…


#182

Love that Kane is up there. Not enough top class English footballers about these days. Surprised at Suarez though, thought he was far better.