He doesn't need to pull a "complete 180" on defense.
If he can get to being even average as a defender, he will easily outscore his deficiency's in that end. We are talking about one of the premier offensive players in the game.
To borrow some baseball nomenclature - get from being 70 grade offense, 35 grade defense to 70/45 and that's a supremely valuable player.
I also think usage isn't spoken of enough - he shouldn't be playing 28 min a night, its easier to defend with legs that aren't primarily composed of lactic acid.