Interestingly since the home game against Stoke where he scored the only goal of the game, in all the games he's started we've only scored one goal with him on the pitch, and three goals once he's been subbed off.
Off the top of my head from the fixtures before that there was:
the Sunderland game which was a freak result, but we scored 3 goals after he came on off the bench.
Spurs away where he started, missed a sitter, and we didn't score.
I think there really is something to the theory of him disrupting the balance of the team.