Expected Passing - the @footballfactman model
Can you really tell if someone is good at passing?
One of the biggest criticisms of football stats is the use of pass completion as a metric.
Anyone can complete 100% of passes if they only pass sideways or backwards.
Would 40% completion from 5 passes be good? What if the two that succeed are defence splitting passes that result in two goals? Isn't that better than 50 accurate passes that create nothing?
So how could you measure passing ability?
Perhaps if you had the X/Y coordinates for every pass.
You could then look at the completion rate of passes from X/Y to X/Y.
The completion rate would give you a difficulty rating for that pass, under typical circumstances.
So a pass from centre back to centre back would probably be completed 99/100 but a cut back pass within the opposition box may only be completed 20/100.
You could then work out the expected passing rate of every pass played by a player, and the average difficulty of the passes they played.
These passes could then be grouped to make it even clearer what type of passes the player is attempting. For example a wide defender may make lots of simple passes in their own half, but crosses when in the opposition wide areas. It should too be obvious which strikers drop back into central attacking zones and try passes through the middle, and which control the ball and pass it out wide.
Yes, you don't need a spreadsheet to tell you that Aguero is a better passer than Lukaku. But do you know every player in every league?
Sounds like a lot of work to do though. And would it actually work?
Well luckily Paul Riley (@footballfactman) has already done the work, and I have been lucky enough to have access to a version of it to try it out.
So sanity check one.
We'll compare Lukaku with Aguero.
Lukaku has made 210 out of 296 passes. The models says he should have made 220. So he has an xP rating on 0.95. His average pass had a usual completion rate of 74%.
Aguero has made 448 out of 525 passes. The model says he should have made 430 so he has an xP rating of 1.04. His average pass has a usual completion rate of 82%.
So we can see that Lukaku is making more difficult passes, but less well than the average player and Aguero is making easier passes at a better than average rate.
If we look at where they make their passes from and to we see they are in central areas mainly although Lukaku often plays passes from wider areas. I added Salah into check this and he shows up with having more wide and less central involvement so I think this works too.
We can also look at the team model.
Top of the list are Manchester City with an xP of 1.05 and an average usual pass completion rate 85%
Bottom are Cardiff City with an xP of 0.93 at an average usual pass completion rate of 73%.
No surprises there really but again I think that just shows it is right.
If we look at Liverpool against Manchester City I can see that Liverpool play a lower average success rate pass than City, indicating they are going for slightly riskier or longer passes.
Comparing squad with squad:
The first thing to note is that both these teams are really good at passing. Only two players are *just* below the model average; Saido Mane and Trent Alexander-Arnold, both of whom are playing a high proportion of risky passes.
Sane and Sterling show up as players who play risky passes brilliantly.
I always have to check Messi, and yes, he shows up as a brilliant passer completing well above xP on difficult average passes.
It also completely backs up my theory on Everton's passing being a significant issue in the forward areas.
So how about some random names the model picks out, these are players I've barely seen so let me know if they make sense or not:
Aissa Mandi of Betis
Boubacar Kamara of Marseille
Jonathan Schmid of Augsburg
Daniel Congre of Montpellier
Pierrick Capelle of Angers
Paul (@footballfactman) has developed a great model, there is also lots more that could be done with the data, it would particularly suited for some data visualisation work.
One of the biggest criticisms of football stats is the use of pass completion as a metric.
Anyone can complete 100% of passes if they only pass sideways or backwards.
Would 40% completion from 5 passes be good? What if the two that succeed are defence splitting passes that result in two goals? Isn't that better than 50 accurate passes that create nothing?
So how could you measure passing ability?
Perhaps if you had the X/Y coordinates for every pass.
You could then look at the completion rate of passes from X/Y to X/Y.
The completion rate would give you a difficulty rating for that pass, under typical circumstances.
So a pass from centre back to centre back would probably be completed 99/100 but a cut back pass within the opposition box may only be completed 20/100.
You could then work out the expected passing rate of every pass played by a player, and the average difficulty of the passes they played.
These passes could then be grouped to make it even clearer what type of passes the player is attempting. For example a wide defender may make lots of simple passes in their own half, but crosses when in the opposition wide areas. It should too be obvious which strikers drop back into central attacking zones and try passes through the middle, and which control the ball and pass it out wide.
Yes, you don't need a spreadsheet to tell you that Aguero is a better passer than Lukaku. But do you know every player in every league?
Sounds like a lot of work to do though. And would it actually work?
Well luckily Paul Riley (@footballfactman) has already done the work, and I have been lucky enough to have access to a version of it to try it out.
So sanity check one.
We'll compare Lukaku with Aguero.
Lukaku has made 210 out of 296 passes. The models says he should have made 220. So he has an xP rating on 0.95. His average pass had a usual completion rate of 74%.
Aguero has made 448 out of 525 passes. The model says he should have made 430 so he has an xP rating of 1.04. His average pass has a usual completion rate of 82%.
So we can see that Lukaku is making more difficult passes, but less well than the average player and Aguero is making easier passes at a better than average rate.
If we look at where they make their passes from and to we see they are in central areas mainly although Lukaku often plays passes from wider areas. I added Salah into check this and he shows up with having more wide and less central involvement so I think this works too.
We can also look at the team model.
Top of the list are Manchester City with an xP of 1.05 and an average usual pass completion rate 85%
Bottom are Cardiff City with an xP of 0.93 at an average usual pass completion rate of 73%.
No surprises there really but again I think that just shows it is right.
If we look at Liverpool against Manchester City I can see that Liverpool play a lower average success rate pass than City, indicating they are going for slightly riskier or longer passes.
Comparing squad with squad:
The first thing to note is that both these teams are really good at passing. Only two players are *just* below the model average; Saido Mane and Trent Alexander-Arnold, both of whom are playing a high proportion of risky passes.
Sane and Sterling show up as players who play risky passes brilliantly.
I always have to check Messi, and yes, he shows up as a brilliant passer completing well above xP on difficult average passes.
It also completely backs up my theory on Everton's passing being a significant issue in the forward areas.
So how about some random names the model picks out, these are players I've barely seen so let me know if they make sense or not:
Aissa Mandi of Betis
Boubacar Kamara of Marseille
Jonathan Schmid of Augsburg
Daniel Congre of Montpellier
Pierrick Capelle of Angers
Paul (@footballfactman) has developed a great model, there is also lots more that could be done with the data, it would particularly suited for some data visualisation work.
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