I believe the GE is sophisticated enough that there is no one simple factor to explain a player's performance.
Amongst the good hints already given to ShohokuZ I added one I thought worthy.
As y2bulldog pointed out, it's specifically in the last game the shooting percentage was horrible and also a second game on the 4th.
This player is used as a back up and usually plays 15-20 mns a game. When his time on court goes up, his shooting % dramatically goes down.
I am not funny. Never ;) If his atrocious stamina takes no part in his performance when playing 61 minutes in one game then having a stamina skill is very silly.
Here is the player in scrutiny
(9493696).
I hope it's now elaborated enough for you.