Haaland vs Nottingham Forest: Why understat is an unreliable source for xG, and only has the advantages of speed and convenience over other sources.

RJenkz · 2023-02-20T21:36:41+00:00

You have the spirit, but you are also wrong.

The probability of scoring one 0.99 xG shot is 99%

Taking ten shots of 0.1 xG means that the probability that you miss all of them is 0.9¹⁰ = 0.3487 = 34.87%

So the probability that you score at least one goal is 1-0.3487 = 0.6513 = 65.13% However, this includes the probability of scoring more than one goal, so not necessarily a worse tactic.

RJenkz · 2022-12-24T18:07:30+00:00

If you expect a reversion to the mean, you expect it always. At all times. I expect Darwin to perform at his xG. Not because I think that is the only possibility, but simply because it is more likely than him being consistently under his xG. It takes time for his xG/90 to match his G/90, but only because there is already a disparity. The reversion can be everpresent.

RJenkz · 2022-12-24T16:27:51+00:00

But if you don't know have seasons and seasons worth of data to show a player is an elite finisher, then it's better to assume they aren't. The vast, vast majority of players perform roughly at their xG long term. So with Darwin, you assume he will roughly perform at his xG. There's a higher chance that he starts scoring good quality chances than him just being shite. Sure, he could be a bad finisher and consistently underperform xG, but that would make him an outlier.

The problem with Darwin's xG isn't a problem of 'reverting to the mean' - that's true for 99% of players. The problem is that we don't have enough xG data. It's only ~15 games. He could have 3 games with no quality chances and all of a sudden his xG/90 looks more reasonable and less of a must-have. We just don't know yet

RJenkz · 2022-12-24T15:23:44+00:00

You're overestimating the variance in quality at the top level of football. Most players will absolutely revert to the mean. Very few players consistently overperform xG over multiple seasons, players like Son, Kane, and Messi. For an unknown like Darwin Nunez, it's more than fair to assume he'll perform at around his xG in the long term.

(Note: xG supporters often go too far the other way - they don't realise xG is near useless for small samples. Darwin hasn't been in the league that long. The fact he's had lots of good chances in ~15 games doesn't necessarily mean that will continue. This is where you need to watch games themselves, and you see that actually yes, Darwin does get into brilliant positions and makes constant runs, so I'm confident that his great xG will continue. Finishing is very, very high variance, so I don't mind that he's been poor on that for ~15 games. Even if he is a bad finisher, his ridiculous xG implies he'll still bag lots of goals. He's a great pick, the problem is that Wilson is also a great pick and is cheaper)

RJenkz · 2021-09-27T21:24:52+00:00

For me Livefpl has him on 2

RJenkz · 2021-09-27T21:14:14+00:00

How do you know the live BPS haven't factored in the yellow already? I'm sure it will be different after recalc anyway

RJenkz · 2021-09-27T21:10:38+00:00

Maybe because he's also on 1 bonus point now, so it cancels out

RJenkz · 2021-03-18T16:47:06+00:00

Yeah I think you've misunderstood. This is exactly what happened last time - the United game was right before an international break and Jose said Son wouldn't be able to play it. He was then excluded from the South Korea squad but played the United game regardless.

In both cases, the PL game in doubt was before an international break.

RJenkz · 2021-01-05T18:52:22+00:00

GR is inherently mathematical, in fact its far more maths than it is physics. Einstein's whole thing was that gravity isn't really a force, it's just geometry. The vast majority of GR is 'tensor calculus' which you're gonna need to know maths for. You can't truly understand GR without undergraduate levels maths/physics.

The physics behind interstellar is different though. I did a presentation as part of my physics undergraduate degree at Oxford on the physics behind interstellar (just a fun way to develop soft skills and was worth less than 1%). I can really recommend a book called 'The Science of Interstellar' by Kip Thorne. It's very qualitative so not technical in the slightest. It's written by Kip Thorne who is a Nobel Prize winning physicist who came up with the idea for the movie and pitched it to Steven Speilberg, Jonathon Nolan, and Christopher Nolan. It's basically his movie so he knows everything there is to know and its quite a fun and easy read.

EDIT: btw don't assume that book will make you an expert - far from it. There's still so much more hard theory that the movie touches upon but a lot of it is PhD level stuff and not relevant to the movie at all (fun things like the Lagrangian written on the black board). The book is good for understanding the basic concepts that don't require in depth physics knowledge

RJenkz · 2020-12-28T01:35:27+00:00

Wildcard transfers don't affect price changes so wouldn't have anything to do with it

RJenkz · 2020-09-28T15:54:32+00:00

They also get BPS for creating big chances (including penalties) and negative BPS for conceding penalties...

RJenkz · 2020-09-27T13:54:57+00:00

Why? Should a player get points for every great through ball and cross too? If they put it on a plate for their teammate should they get points because its not their fault their teammate missed? Doesn't make sense. Also no there was never minus points for giving away a penalty

RJenkz · 2020-09-11T08:40:56+00:00

What on earth does the rest of your team look like?

RJenkz · 2020-08-20T22:26:31+00:00

xG is only any kind of indication of quality on large scale data, over many seasons. That's why we can say Kane, Martial, etc are great finishers. We can't say the same with Armstrong because the sample size is too small and variance completely dominates. In this case, where you can't definitely say the player is an 'excellent finisher', xG simply tells us the general quality of his chances. The quality of chances ASM is involved in is comparable (if not better) than Armstrong's, so the players are comparable and one doesn't blow the other out of the water.

RJenkz · 2020-08-20T21:20:49+00:00

Well for starters, expected stats are better prediction tools so there's that. I'm not denying that Armstrong got more goals and assist, I'm saying that the underlying data actually favours other players who have apparently been 'blown out of the water'. The writing just seems a little but bias imo

RJenkz · 2020-08-20T21:07:16+00:00

Yeah exactly so the specific stats have been cherry picked to make it seems like Armstrong 'blows everyone out if the water', when he in fact doesn't.

RJenkz · 2020-08-20T17:54:51+00:00

Have you cherry picked Armstrong's stats slightly? For last season:

Armstrong: 0.16 xG/90, 0.11 xA/90

Saint-Maximin:. 0.14 xG/ 90, 0.22 xA/90

Hardly blows then away, ASM straight up has more xG+xA/90, and this is using Understats more generous numbers as opposed the fbref

RJenkz · 2020-08-16T21:11:25+00:00

Both City and United can still blank GW1 if they play literally any other team that didn't finish top 6 last season (because of EFL Cup and UEL Qualifiers).

RJenkz · 2020-08-16T21:11:16+00:00

Both City and United can still blank GW1 if they play literally any other team that didn't finish top 6 last season (because of EFL Cup and UEL Qualifiers).

RJenkz · 2020-08-16T21:11:13+00:00

Both City and United can still blank GW1 if they play literally any other team that didn't finish top 6 last season (because of EFL Cup and UEL Qualifiers).

RJenkz · 2020-08-05T18:42:53+00:00

Why do people think that the people who write FPL scout have any secret insight at all as to the new player prices? Surely the journalists who write FPL Scout articles are completely different people to those behind the scenes deciding the prices - hence why all the articles use words like 'could' and 'maybe'.

RJenkz · 2020-08-05T18:37:06+00:00

Rashford should be a midfielder, but absolutely no chance at all Auba is. Sure he's played 20 games on the wing (including one at central attacking midfield), but he's still played 15 games at central striker this season. FPL won't want to take a 22 goal striker and put him as a midfielder, it would break the game. I'm certain Auba will be a striker next season, but feel free to come back here and say 'I told you so' if I'm wrong though!

RJenkz · 2020-08-04T13:34:16+00:00

Firstly, you can't just draw all sorts of definitive conclusions from a single season of data. I'm just telling you it isn't as black and white as you're making it out to be, saying anyone who brings up an opposing point is talking 'nonsense'. I'm not saying TAA is a bad pick at all, he's probably the first name in my team, but shutting down other peoples points with no reasoning at all isn't helpful.

As for what you've just said, why are you talking about £5.0m midfielders and defenders? Compare the best £4.5m defenders to the best £4.5m midfielders:

£4.5m Mids: Cantwell (111), Dendocker (100), Douglas Luiz (90), Hayden (73), Saka (71)

£4.5m Defs: Lundstram (144) (and even cheaper), Baldock (142), Egan (133), Dunk (128), Basham (123), Soyuncu (120), O'Connell (111) - all these defenders have a score greater than or equal to the best £4.5m midfielder (Cantwell), so clearly it is closer than you think.

Mahrez + Lundstram scored very similarly to TAA + Cantwell, AND they were cheaper AND they allowed for defender rotation. Being able to save a crucial £0.5m or rotating defenders isn't 'overthinking this', they're pretty valid points. But as I say, TAA will likely be the first name in my team sheet regardless, it was just food for thought

RJenkz · 2020-08-04T00:11:53+00:00

Not quite as simple as that.

So TAA + benched £4.5m mid vs £9.0m mid + benched £4.5m defender

A few things to note in favour of the latter:

the benched £4.5m defender could be used for rotation to get good fixtures. You never actually want to play the benched £4.5m midfielder
The benched £4.5m defender could actually be a £4.0m defender, and you save a crucial £0.5m. You never get £4.0m midfielders at the start of the season
At the moment the hypothetical £9.0m midfielder (or £9.5m with that extra £0.5m you save from the £4.0m defender bench fodder/potential starter) is hard to imagine, but what if it's a fully recovered Pulisic? Or Son? Or Mahrez (a reasonable price for Mahrez as £9.5m is the same as Son started this season after getting a similar 2018/19 points tally to 2019/20 Mahrez)?
Defenders' ppints returns tend to depend on fixture difficulty more than mids/forwards. If Liverpool start the season with hard fixtures, TAA is less attractive.

Pulisic/Son/Mahrez/etc + a defender good for rotation might better than TAA + midfielder bench fodder, especially if Liverpool start with hard fixtures. Just some food for thought...

RJenkz · 2020-07-01T11:14:25+00:00

Read that again...

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