I think that highlights one of the key issues with xG it is a pure mathematical model based on shooting positions. Scoring goals is hugely dependent on the mental side of things more specifically a player's confidence. In general confident strikers do better against their normal conversion rate whilst strikers low on confidence underachieve.
Confident strikers make easy chances look difficult, whilst strikers who are low on confidence often do the opposite. Personally I think the problem is how reliant we are on Bobby performing well. I think we need to come up with more viable options when Bobby isn't performing at his best. Take the pressure of Bobby
As I posted - he’ll revert to the mean next season and people will post endless nonsense about him ‘getting his confidence back’
xG works not because someone thinks it’s a good idea but because it’s correlative and predictive over time.
It’s not a perfect correlation and it can be (and is being) improved... but over time players taking shots achieve the same results from the same positions. A few players can over achieve their xG or under achieve it .. but the margins over time are narrow
Therefore if we see a player like Firmino whose hit is xG more or less over his career having a freak spell of not finishing we can be pretty sure as night follows day that he’ll revert to the mean
The idea of confidence in finishing is one of the most over blown in football.
Maybe it can affect how many shots a player takes (Firmino is actually taking slightly more than last year) but the idea that a professional players mental state is the governing factor in the direction and velocity a ball takes off their boot in the micro seconds of time it takes to kick a ball is pretty fanciful
It’s one of those belief systems that’s simultaneously both not provable of disprovable.
xG is provable / disprovable / critiqueable by test - confidence levels are entirely supposition
