His problem has always been not having the right attitude on (and probably off, looking at what he said to Alessio last year) the pitch.
I mean, when he plays he's always complaining like a little bitch for not passing/a pass in a different way/a choice from another player/his mother/whatever. It happen even to other players, but he does it consistently and also for bullshits. For example last year against Chelsea, Lichtsteiner gave him a ball, he missed and started complaining explicitly with big gestures and an angry face to Licht like if he gave him a shit ball

Or you get subbed in a shitty match (ok, the whole team played shitty that night, but it does not matter) and you cover your mouth with your jacket probably saying a bad thing to Alessio (who's not even your real coach, thatis a bit cowardish cause nobody have the guts to say that to the Boss). He's been lucky to not get kicked out of the squad cause last year he was still important for the team. If it happened this year he'd be kicked out like Amauri, Iaquinta and Grosso were.
He's always been a quite technically and tactically gifted player, and he's improved a lot in his late 20s. But since Conte is there he's got a really bad attitute, he probably feels unappreciated but can't behave like that.