He's not the quality required at United, and that is being sorted out now by the management. Injuries haven't helped him. He's been completely overawed by it all. But at least he has tried to adapt to a new role, in a new environment. He's not good enough. That's it at United.
At Everton he was an excellent player for them. He started off as a defensive minded midfielder next to Arteta and it was only when Cahill departed that he got pushed further up. It seems people have short memories of his time at Everton because a.) he is the personification for the Moyes era and b.) his success at Everton was under Moyes so we all want to believe it was complete long ball, chest, head, elbow playing style. That's not the case