When The Jazz picked up AJ I watched a great deal of video and I can tell you for sure that the explosiveness is not there yet. Granted he's no Karl Malone but I think as the season goes on and he gains more confidence you'll see him attack the rim a lot more.
Im guessing the same thing...I think in the back of his mind, he is still playing with an injury. He needs to get past that for that alone can hurt him.