Ole and xG

Pogue Mahone

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I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

 

Tarrou

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where do people get the xG stats from? Is the above confirmed to be correct?

Would be interesting to know what Fergie's teams looked like.
 

Samid

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We score more than 'expected' because we have some good attackers. We concede less than 'expected' because we have the best goalie in the world.

xG is completely bollocks without context.
 

rotherham_red

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xG is just another example of using stats that are devoid of all context.
I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

 

Hawks2008

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Viewing football through the lens of xG is silly, I know the football hipsters on reddit love to circlejerk about it's really quite meaningless.
 

deafepl

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As I've said before, the stats mean nothing, Arsenal, Chelsea and Fulham had a higher expected goal than us when we played them but if you watch the game, you'll know we're a well drilled and better team over 90 minutes.

Spurs are only one game I can think of us getting outclassed in the last 30 minutes.
 

Rajma

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Does it take into account all the injures? If not then it's a pointless stat. Would make sense to compare pre-injury spree xg and during the injury crisis.
 

space

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Think if looked really simply, Ole has encouraged our players to shoot more, so we are scoring more from outside the box, deflections becauase we are risking more

Also DDG in goal is awesome

I think Zidane must have had a similar xG at Madrid in 16/17
 

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This thread will go well:lol:
 

Pogue Mahone

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where do people get the xG stats from? Is the above confirmed to be correct?

Would be interesting to know what Fergie's teams looked like.
Yer man seems legit. He works for Opta.

No idea how we looked under Fergie. He posted xG under Mourinho.

 

Anustart89

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I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

It says feck all. The expected goals being lower than the actual goals could be due to a lot of factors, two of them being our players performing better than expected in front of goal, opposing defenders and goalkeepers underperforming in comparison to the expected average.

The expected goals against, similarly, could be due to a goalkeeper that is much better than average (which we have), or opposing attackers missing easy chances due to being shit.

What I don't get is that it's an aggregation of tens of thousands of situations, so really the only team that would be matching their xG/xGa stats would be an average team sitting in tenth place in the league. Shouldn't an above average team be expected to perform higher in the xG department (due to having better than average attackers) and lower in the xGa department (due to having better than average defence/keeper) by default? Yet the common interpretation is that outperforming your xG is somehow an indication of jamminess or a good vein of form where the bubble is going to burst any second. One article even said that Ole should say no to the United job because he's outperforming the xG stats by so much that he can only go down from there, which I found ridiculous.
 

EwanI Ted

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xG needs context. Same way that 70% possession can mean you totally dominated a team, or could mean you passed it back and forth between your defenders without hurting them. Or how having made very few tackles could mean your defenders are timid, or it could mean they're excellent at reading the game.

I still prefer xG to shots on/off target, but in all cases stats should be used to illustrate a point, not be adhered to slavishly.
 

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Its about the likelihood of a shot being scored based on its difficulty. The top strikers in the EPL score more than xG so its not that its not sustainable just that they are top class players who can make difficult finishes regularly.
 

Cait Sith

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It isn't meaningless. It's actually one of the more solid statistics out there. Just because you don't like what it says doesn't mean it's bullshit.
 

Skills

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where do people get the xG stats from? Is the above confirmed to be correct?

Would be interesting to know what Fergie's teams looked like.
Why Fergies teams specifically? It's almost another era. Don't think the stat even existed then.

Last season city had an xG of 91 goals and ended up with 106 real goals.

I do think it actually just shows what we've been seeing but some people are a little blinded by the good feeling factor at the moment. We don't really carve up teams the way for example City do, but we do have a fantastic set of players who can produce a lot and are very efficient. To become better next season (and hopefully with a full pre-season of training), just buying better players isn't enough. We need Ole and his team to develop the system a bit more so we can get even more out of the players at their disposal.

Post Mourinho - so far it's just been phase 1. Get the shackles off and release their attacking instincts. 2. Is maximising the potential at hand.
 

Andersons Dietician

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I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

I quite like XG, However you look at that expected goals against and then think to the Spurs game and it probably makes up most of that.

It works off of areas of danger or high percentage scoring zones. Personally think it gives a better picture than just hardcore stats.
 

bosnian_red

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So we have ~30xG goals and they take out penalties from that total, so add 6/7 and you'd expect 36. We scored 38. No difference basically. Anyway, xG doesnt capture chances that dont result in actual shots. Could dribble past the goalkeeper but it goes out of play, no xG change.

Goals conceded, its De Gea, he always outperforms xG.
Secondly, game state isnt captured by xG. Example is Fulham-United being 2-2 on xG even though we hammered them, because once we were 3-0 up we got relaxed and they ended up having an open net chance that was basically a full 1. Multiple times that happens. Goals change games.
Third, player quality isnt captured by xG. You would expect top players to be more clinical and top goalkeepers to keep out more (de gea was like +15 last season I think).

Lastly, we've had an absolutely insane fixture list after the easy first 3-4 games. Yet we're still getting results along with good performances. Everyone is seemingly ignoring it but in 2 months weve played Spurs away, Arsenal away, Chelsea away, Leicester away, Palace away, Liverpool at home and PSG home and away. Combine that with a feck ton of injuries. Yet we've basically won all of them and still have a respectable xG overall (drew to Liverpool, won the tie vs PSG).
 

kundalini

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I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

There is a huge misunderstanding about Expected Goals.

Name an elite team that is performing well this season (Man City, Liverpool, Dortmund, Barcelona etc etc) and you will see that they are massively out-performing their expected goals numbers. In the table linked, green is better than expected, red is worse. https://understat.com/league/EPL/2018

Likewise, the teams at the bottom of the table will typically have been a bit unlucky, missed good chances to score in some tight games they ended up losing or drawing.

It's not just this season, it is true of most seasons. When Chelsea won the title under Conte, their expected goals for was 61.80, yet in reality they scored 85. Their expected points 75, in reality 93. Spurs finished 2nd. They too massively out-performed their expected numbers. City last season scored 14 more than expected, and got 9 more points than expected.

This may comes as a huge shock to you but elite players when performing well tend to finish chances at a better rate than an average player would. Elite keepers save shots that many other keepers wouldn't.

If you go through the individual games, Expected Goals didn't like the performances against Spurs and Leicester, matches in which United scored in the first half then sat deep and defended for the rest of the match. In contrast, the Burnley game in which we were 0-2 down, looks like it should have been an easy win for United as we created several big chances to score.

Based purely on chances, the Fulham match could have been a draw, yet anyone watching will have noticed that Fulham had several opportunities in the first 10 mins then almost nothing until the score was 0-3. Ryan Babbel's big chance after 76 mins when he hit the post from close range, was worth 0.59 xG (on average, out of 100 shots from that position, you'd score 59 times). Yet even if he had scored, Fulham would still have struggled to get a draw in the time remaining.
 
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Pogue Mahone

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So we have ~30xG goals and they take out penalties from that total, so add 6/7 and you'd expect 36. We scored 38. No difference basically.

Goals conceded, its De Gea, he always outperforms xG.
Secondly, game state isnt captured by xG. Example is Fulham-United being 2-2 on xG even though we hammered them, because once we were 3-0 up we got relaxed and they ended up having an open net chance that was basically a full 1. Multiple times that happens. Goals change games.
Third, player quality isnt captured by xG. You would expect top players to be more clinical and top goalkeepers to keep out more (de gea was like +15 last season I think).

Lastly, we've had an absolutely insane fixture list after the easy first 3-4 games. Yet we're still getting results along with good performances. Everyone is seemingly ignoring it but in 2 months weve played Spurs away, Arsenal away, Chelsea away, Leicester away, Palace away, Liverpool at home and PSG home and away. Combine that with a feck ton of injuries. Yet we've basically won all of them and still have a respectable xG overall (drew to Liverpool, won the tie vs PSG).
That's a very good point.
 

acnumber9

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It’s being used as a method to say a team are being lucky. The best teams should be scoring more and conceding less than they’re ‘expected’ to. It’s a load of balls in short.
 

Raees

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Tbh I agree with the XG stat and it confirms to me that whilst we have undergone a renaissance under Ole under the microscope the actual quality of the football hasn’t really been that great.

It’s just that the football under Jose was that shit, we look miles better but it’s more between the ears where Ole has performed miracles rather than actually tactically/technically where I still think we fall short of Europe’s elite.

We’ve riden some luck as well but when you’re feeling positive and you fight to the last whistle then things will go in your favour. We’re getting results which the ‘quality of our football’ doesn’t merit but our heart does if that makes sense.
 

jojojo

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Is this is all just a complete load of bollox? Does it tell us anything useful at all?
I think it does tell you something about playing style, which for the moment isn't dramatically different in terms of build-up play. What it doesn't tell you is the speed at which the build-up is done, the confidence/ability of the individual players involved, and the extent to which opposing defenders are being distracted/panicked into making errors.

Like last night - Rashford was drawing the attention of defenders, the forward pairing were hunting together, confusing the defenders, allowing Lukaku to take advantage. Lukaku is going back to his best playing style - forward facing, ball on the floor - and with that type of chance he scores more than when given the wrong kind of (allegedly easier) chance.

Same at the back. The defenders are playing well. Strikers may be getting the chance but they know our defenders are close and closing and they're losing their belief in the odds.

So yeah, our "better than xG" numbers probably tell us that individually our players are good, that they're now playing a style that suits them better and that they're playing well. It also tells you that with time to develop our play, we'll get better.
 

Bola

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Bollocks stat and who cares apart from butter Liverpool fans trying to make themselves feel better?
 

adexkola

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First of all if you think xG is shit then jog on, this post isn't for you.

We've seen results go against xG for a season, but from my recollection, results always regress to the mean. 2 examples come to mind:

1. Guardiola's first season, their results were worse than xG would suggest. Based on that, some people predicted they would win the league the following season, they did, by a mile.
2. The season that we finished second, we conceded less goals than xG suggested. DDG had an outstanding year of course. Was it any surprise that results dipped the following season?

If the numbers are saying we should be conceding more and scoring less, then it's worth looking into, and making the correct adjustments, before next season. Regardless, Ole has done well enough to be given a chance to look into making sure this run of form isn't a blip.
 

Charlie Foley

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I'm probably being a bit self-indulgent but the Ole thread is so busy this specific topic might get lost. Why are xG painting such a grim picture of his time in charge? Is it unusual to have such a massive disconnect between xG and the actual points on the table? Is this is all just a complete load of bollox? Does it tell us anything useful at all?

It tells us we’ve a great keeper and have scored some great goals in his time here-probably because he’s got our forwards shooting with confidence
 

dove

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To be fair we had similar stats last season where we clearly won more points than we should have. We had some unconvincing games under Ole as well, like against Southampton, Crystal palace and Spurs where we won 9 points but we could have easily lost all of them on the other day. We still have to improve especially in maintaining the possession and we still concede way too many chances. I am just praying we finally sort out our right side in the summer because majority of our problems are here.
 

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Like any stat, it need to be contextualised for it to mean anything relevant to you. If you can't/don't want to understand what a stat is supposed to be representing and see it's shortcomings, you should probably just stay away from looking at them.
 

bosnian_red

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That's a very good point.
You would expect xG in those games overall to be pretty even at best. It's all about being decisive in those with small margins being the difference and we have been. That's the main disconnect between current xG and our play.

Either way, I like xG but it is very imperfect and theres way too many things unaccounted for like I mentioned before. Game state/player quality/chances that end without a shot being the 3 main ones IMO. Can also throw in theres no model that can accurately assess how a player is being pressured before he takes a shot on. They try, but it's impossible.
 

VP

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Sample size is still too small. This is heavily distorted by our games against PSG.

Looking at our league games under Ole: we've scored 29 against a xG of 25. Liverpool also have a similar gap (+3) and Spurs an even greater one (+6).
 

bosnian_red

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To be fair we had similar stats last season where we clearly won more points than we should have. We had some unconvincing games under Ole as well, like against Southampton, Crystal palace and Spurs where we won 9 points but we could have easily lost all of them on the other day. We still have to improve especially in maintaining the possession and we still concede way too many chances. I am just praying we finally sort out our right side in the summer because majority of our problems are here.
XG had us hammering Burnley and Southampton though while we dropped points to Burnley and needed the late winner. In the games we expect to win, our xG has been pretty much as youd expect bar a couple where random moments skew it (but are easily explained like the Fulham game). Weve grinded out a lot of tight wins but being able to maintain that level across the ridiculous run of fixtures is a good thing in itself which they ignore.
 

Pogue Mahone

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There is a huge misunderstanding about Expected Goals.

Name an elite team that is performing well this season (Man City, Liverpool, Dortmund, Barcelona etc etc) and you will see that they are massively out-performing their expected goals numbers. In the table linked, green is better than expected, red is worse. https://understat.com/league/EPL/2018
Arsenal are the only team on that table with an xG that is >10 more than their actual goals. City and Liverpool are <5.

And that table is based on 29 games. We're currently >10 after just 17 games.
 

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We had this discussion about a week ago.

When you actually broke down the points xG awarded for each shot it started to not make much sense. I wouldn't go as far as saying its a load of shit, but it needs refining as some of the shots it was claiming were easy were in fact not easy at all when viewed. It also doesn't seem to take into consideration whether the player taking the shot has his view blocked by opponents, it also doesn't seem to take into consideration opponent pressure.

It's extremely flawed right now and anyone using it as evidence frankly doesn't understand how football works and should be laughed at. Repeatedly.
 

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How is it calculated?
This was my question to. I havent seen an explanation so I looked it up.

"Expected goals" is a metric which assesses every chance, essentially answering the question of whether a player should have scored from a certain opportunity.

Put simply, it is a way of assigning a "quality" value (xG) to every attempt based on what we know about it. The higher the xG - with 1 being the maximum - the more likelihood of the opportunity being taken.

So if a chance is 0.5xG, it should be scored 50% of the time.

Football data experts Opta have analysed over 300,000 shots to calculate the likelihood of an attempt being scored from a specific position on the pitch during a particular phase of play.

The factors taken into account when assessing the quality of a chance include:

  • Distance from goal
  • Angle of the shot
  • Did the chance fall at the player's feet or was it a header?
  • Was it a one on one?
  • What was the assist like? (eg long ball, cross, through ball, pull-back)
  • In what passage of play did it happen? (eg open play, direct free-kick, corner kick)
  • Has the player just beaten an opponent?
  • Is it a rebound?
https://www.bbc.co.uk/sport/football/40699431