Expected Goals - useful or a load of old nonsense?

[jamesha]

Over the past few years "Expected Goals" seem to have become a big thing and have even been used to claim that the league table is an aberration and that we should be level or higher than Liverpool.

I had some interest in this so downloaded the Kindle sample of "The Expected Goals Philosophy: A Game Changing Way of Analysing Football" by James Tippett. The link below goes to Amazon where you can preview the book.



I found the preview pretty dull and the smug attitude of the writer put me off and he was seeming to claim that this method was revolutionary and would improve football performance massively for clubs/coaches that bought into it.

I am sceptical of this but would be interested to hear the views of other bluemooners. Has anyone looked into this in depth - maybe for betting purposes?

 

[Vienna_70]

I expected goals a load of bollocks.

But that is a personal opinion and not necessarily that of most people.

 

[domalino]

Expected Goals is an incredibly good statistic, but people use it incorrectly, and it's still very "young", so it will get better as it gets refined and more complicated.

The best use of it IMO is not out and out xG, but in xG chains and xG buildup which is a way of measuring how often a player is involved in the build up, how often they start or participate in moves which end in big chances.

With regards to books, I've been told the Christoph Biermann book Football Hackers is very good, but haven't read it myself.

 

[Ban-jani]

Useful.

I only pay attention for City games but it seems to correlate as being high for games we’ve created a lot of chances in and vice versa for when we’ve had an off day.

 

[daztrueblue91]

I think it’s a useful stat when looking at the general pattern of matches.

There have been matches we have lost/failed to win this season which have been a travesty.

It’s difficult to blame the gaffa or the tactics when we are comfortably making 5/6 x the clear goal scoring chances as the opposition but failing to score.

Even against Villa in the final, we were a wonder save from it going to ET/penalties. That was despite dominating the game for 80 mins.

 

[Pablo ZZZ Peroni]

Over the past few years "Expected Goals" seem to have become a big thing and have even been used to claim that the league table is an aberration and that we should be level or higher than Liverpool.

I had some interest in this so downloaded the Kindle sample of "The Expected Goals Philosophy: A Game Changing Way of Analysing Football" by James Tippett. The link below goes to Amazon where you can preview the book.



I found the preview pretty dull and the smug attitude of the writer put me off and he was seeming to claim that this method was revolutionary and would improve football performance massively for clubs/coaches that bought into it.

I am sceptical of this but would be interested to hear the views of other bluemooners. Has anyone looked into this in depth - maybe for betting purposes?

I use it extensively (with loads of other stats/analytics) for interest, analysis and betting. It is invaluable IMO. There have been threads about it on here before but not much interest.

Have a play on understat.com and see a selection of different types of data including xG Chain and xG Buildup,

Here is a timeline for our game yesterday: https://understat.com/match/11970

I posted the bit below on the postmatch thread last night for some context:

A freak result considering the opportunities, including 5 big chances as defined by OPTa, due poor finishing, good goalkeeping, good defending and bad luck or randomness with all the deflections and blocks.

City xG was unsurprisingly more than 3. So what? Well, the probability of winning with xG>3 in a game is very high.

xG of 3 or more is also not particularly common in the PL. This season:

Liverpool 3 times
Leicester 3
Chelsea 2
United 1
Wolves 0
Arsenal 0
Spurs 1

So 10 times in total for those 7 teams.All resulted in wins and total goal tally was 35 in real life goals and 5 conceded. An average of 3.5 real goals scored and 0.50 goals conceded.

But City are the masters of big numbers for xG. Whilst those teams managed it 10 times combined, today was the 9th time this season alone. A real indication that we create chances like no other team.

In 17/18 we did it 7 times, winning all 7 with 44 goals and 4 conceded.
In 18/19 we did it 8 times, winning all 8 with 29 goals and 3 conceded.

In 19/20 we've now won only 6 of the 9 times >xG 3.00 and scoring 26 in the 6 wins and only conceding 2.

Aside from the freakish loss today, the other 2 were the draw and loss against Spurs where we were v v good in both games but didn't get breaks.

Shit happens. Better today than last Thursday.

 

[Vienna_70]

Expected goals has nothing at Ll do do with actual goals.

So we created a lot of chances yesterday. We didn’t score; Southampton did and we lost.

I really don’t get the point of xGoals.

 

[cleavers]

I only pay attention for City games but it seems to correlate as being high for games we’ve created a lot of chances in and vice versa for when we’ve had an off day.

Don't pay attention to last nights numbers then, you'll only get depressed.

 

[jamesha]

Thanks for the responses. The link that Pablo provided was very interesting. I have replicated part of a table from there with the xg rating of each City player

1 Ederson GK 0.00
2 João Cancelo 0.04
3 Aymeric Laporte 0.11
4 Eric Garcia DC 0.00
5 Oleksandr Zinchenko 0.02
6 Fernandinho MC 0.05
7 Bernardo Silva 0.22
8 David Silva MC 0.84
9 Riyad Mahrez 0.32
10 Gabriel Jesus 1.52
11 Raheem Sterling 0.12
12 Kevin De Bruyne Sub 0.18
13 Phil Foden Sub 0.00

Looking at this Sterling and Mahrez were not doing well so their substitutions were a good move?

From my recollection of the match Dave had better chances than Jesus but the stats suggest otherwise - maybe Jesus had more half chances?

I am surprised by Fern's low score as he came very close to scoring when he hit the post - I assume that it was a very difficult chance.

I will have a look at some other match stats to see if I can relate them to my recollections.

 

[BlueTG]

Another way for an armchair bell end down the pub to think he knows something about the game when in fact he couldn’t tell you what an indirect free kick is awarded for.