He better learn how to play some D first. Dude's rotations are awful and his man to man commitment play to play is similar to Melo's, horrible.
He needs to get in the film room to learn opposing players and offenses tendencies. This will help his rotations and knowledge of where to be when a player he's guarding makes his move. That's the difference between he and Melo and a player like Paul. Paul's just alot smarter on the defensive end. He takes that challenge to improve aptitude in this area. Melo and Amare don't. Being slow to rotate comes from lack of study plain and simple.
This should improve due to increased focus on D by MW but we will see.