[Football] Goal Probability

[Greg Bobkin]

Flicking through the TV channels last night, I stumbled upon the Bayern Munich v Dortmund German cup game. Actually, it was the half-time interval, during which they showed a series of 'most surprising' (or something) goals from Haaland and then some from Lewandowski. This level of 'surprise' was measured as a percentage of 'goal probability', with some of the goals having a gP* of single-digit percentages.

I mean, it was interesting to see, but I have no idea how the stats guys work it out, nor do I really see the point of it apart from being another useless, retrospective stat to create debate about (and start threads on football forums).

Can anyone shed any light on it?


*I have no idea if this is what the shortform is for goal probability, but is seems tedious enough to work.

 

[el punal]

When the Albion play I have my own system :

When the ball crosses the line between the the two sticks it’s ‘YAY!!’

When the crosses the line not between the two sticks it’s “FFS!!”

And that’s all you need to know.

 

[ConfusedGloryHunter]

When the Albion play I have my own system :

When the ball crosses the line between the the two sticks it’s ‘YAY!!’

When the crosses the line not between the two sticks it’s “FFS!!”

And that’s all you need to know.

Good point. The FFS index can also be applied to individual players when they miscontrol the ball or pass to the opposition. And again to managers when they set up with bizarre formations or bring Leon Best on to save a game.

 

[Nobby Cybergoat]

When the Albion play I have my own system :

When the ball crosses the line between the the two sticks it’s ‘YAY!!’

When the crosses the line not between the two sticks it’s “FFS!!”

And that’s all you need to know.

Then 3 minutes later some blokes in a hotel room near Heathrow, make a decision which changes your "YAY", to "FFS"

 

[Postman Pat]

Flicking through the TV channels last night, I stumbled upon the Bayern Munich v Dortmund German cup game. Actually, it was the half-time interval, during which they showed a series of 'most surprising' (or something) goals from Haaland and then some from Lewandowski. This level of 'surprise' was measured as a percentage of 'goal probability', with some of the goals having a gP* of single-digit percentages.

I mean, it was interesting to see, but I have no idea how the stats guys work it out, nor do I really see the point of it apart from being another useless, retrospective stat to create debate about (and start threads on football forums).

Can anyone shed any light on it?


*I have no idea if this is what the shortform is for goal probability, but is seems tedious enough to work.

Goal Probability is actually the basis for xGoals. Every single attempt at goal in the Bundesliga is now given a percentage value. Many factors are taken into account in the calculation: what is the distance to goal? What is the angle for the shot? How many opponents are putting pressure on the player shooting? How is the goalkeeper positioned? How fast is the shooter running? Is he kicking or heading the ball? The quality of the player has no influence at all: whether the player shooting is Robert Lewandowski or an amateur footballer, it makes no difference to Goal Probability. Only when it comes to chance conversion does the individual quality of the player enter the equation.

If you think about it logically, a long-distance shot from an acute angle under pressure from defenders has a much lower Goal Probability than a tap-in into an empty net. The simplest example is a penalty, because it always occurs under the same conditions. The Goal Probability for a spot-kick is always 77 per cent: it's always from 12 yards, there's never any pressure from opponents, with a 37 degree shooting angle, and — based on past experience — 77 of 100 attempts end up in the net. This value is calculated by a 'Machine Learning Algorithm', a form of Artificial Intelligence, which bases its calculation on over 40,000 attempts at goal.

Unlike Goal Probability, xGoals is not given as a percentage, but as a value between 0 and 1 — a penalty, for example, is given as 0.77. The xG values of a team or individual player are now added together. From this total, a statistical statement can be made of how many goals a team or a player — measured by their attempts at goal — should have scored. xG values can be calculated for teams and players within a game, but also for the whole season up to that point.

https://www.bundesliga.com/en/bundesliga/news/expected-goals-xg-and-goal-probability-explained-13847

 

[timbha]

Then 3 minutes later some blokes in a hotel room near Heathrow, make a decision which changes your "YAY", to "FFS"

you are confusing Goal line technology and VAR

 

[Greg Bobkin]

Goal Probability is actually the basis for xGoals. Every single attempt at goal in the Bundesliga is now given a percentage value. Many factors are taken into account in the calculation: what is the distance to goal? What is the angle for the shot? How many opponents are putting pressure on the player shooting? How is the goalkeeper positioned? How fast is the shooter running? Is he kicking or heading the ball? The quality of the player has no influence at all: whether the player shooting is Robert Lewandowski or an amateur footballer, it makes no difference to Goal Probability. Only when it comes to chance conversion does the individual quality of the player enter the equation.

If you think about it logically, a long-distance shot from an acute angle under pressure from defenders has a much lower Goal Probability than a tap-in into an empty net. The simplest example is a penalty, because it always occurs under the same conditions. The Goal Probability for a spot-kick is always 77 per cent: it's always from 12 yards, there's never any pressure from opponents, with a 37 degree shooting angle, and — based on past experience — 77 of 100 attempts end up in the net. This value is calculated by a 'Machine Learning Algorithm', a form of Artificial Intelligence, which bases its calculation on over 40,000 attempts at goal.

Unlike Goal Probability, xGoals is not given as a percentage, but as a value between 0 and 1 — a penalty, for example, is given as 0.77. The xG values of a team or individual player are now added together. From this total, a statistical statement can be made of how many goals a team or a player — measured by their attempts at goal — should have scored. xG values can be calculated for teams and players within a game, but also for the whole season up to that point.

https://www.bundesliga.com/en/bundesliga/news/expected-goals-xg-and-goal-probability-explained-13847

[emoji106]

That's EXACTLY the kind of info I was after.

Nice one, PP!

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