He needs to be dropped to just a squad player for a while. Make him fight for his spot and maybe it'll reignite his hunger.
Two years ago he looked on the verge of stepping up to world class level, but he just hasn't looked remotely the same since that back injury. I don't know if it's the back injury himself that has had an impact on him or whether it's a mental thing (once again possibly related to the back injury or perhaps completely unrelated), but the difference has been so obvious. For most of last season he was managing to still get a good amount of goals and assists which seemed to blind some people to the obvious deterioration in his game, but long-term it was never going to last. He either needed to start playing better, or the end product was going to dry up. Unfortunately it been the latter.