Carmelo might fukk around and see his career end up like Barkley's if he doesn't find a way to become a relentless defender.
He's in the East now and that means having to face the Heat, Celtics, Pacers, Sixers and even Hawks. All good to great defensive teams who have wing players that can put points on the board. That means you're not getting into a shootout against these teams like you did out west. You'll have to put up the points you can get against their defense and then stop them on the other end.
Moving to the East doesn't seem to be such a great move now.
Edit: And its not just Melo either. If Amare had half of Chandler's heart they'd be decent defensively.