This was a big topic on LA radio yesterday. The general consensus seemed to be that he's a) not hurt--or, at least, healed to the point where that's not the issue and b) it's all in his head.
That's not me, that's sort of the radio talking heads here.
They think he's just getting a taste of how it is in the playoffs for the first time, it's overwhelming him, and he hasn't acclimated himself to it yet.
This would make some sense. He seemed completely lost when the refs ran him out of that game in Utah. Some of those calls were bad, most, really, but they came in part from him being out of position and a step slow.
Whether that's injury or just the increased speed of the playoffs I have no idea. But with the general advantage the Lakers have in the West, I see no reason not to throw the guy to the wolves to find out. It can't hurt that much--assuming he's 100% healthy.