Torn rotator cuff in his throwing arm. During the last part of this year he wasn't able to throw the ball but half way towards the infield.
It is a hard injury to come back from especially for an outfielder.
I tore mine earlier this year and it still ain't right. And let me tell you it hurts.
Center Field is deeper in Yanqui Stadium too. He'll probably need to see the team's pharmacist.