Don't doubt your source but I don't think that explains his form. It's not like he isn't trying, if anything he's trying too hard. And he'd be more likely to get a pay rise if he was still scoring.
I actually don't disagree with that in so much as i'm not sure that's the main contributor to his current form however I do think that contract issues led to him taking his eye off the ball and may well have started this downward spiral in his form.