It's not really his fault. It is, after all, Louis van Gaal who picks the team.
But what is his fault is his stupid, cowardly violence. At the end of last season he managed to get himself sent off in a dead rubber against Hull with a dangerous, studs up tackle.
He throws his elbows into the face of opponents, but never an opponent who might give it back. He's just there, swinging away dangerously, either by design or with malice, and often both. It won't be long until he seriously injures someone, and won't be long until he's suspended.
What is also his fault is his inability to pass to another player if he is more than three yards away, and his terrible finishing. He used to be a player, in his Everton days, who would intimidate United players, who would break up their play, and pose a threat in and around the United penalty area. Now, he still does the same, just in a United shirt.=