Didn't he hurt his back in the summer during the championships? It is possible that his body still isn't back to form. He likely has a nagging injury and it's just not being discussed, but I could also be "reaching" here.
Personally, I think it's been the emphasis placed on defense that has "hurt" Bargnani
more than anything. PLaying good defense really drains a person and on offense all you really want to do is rest. Hence, why you take jumpers. It's easier to do that than expound even more energy by taking it hard to the hole. Add in that he's being forced to guard bigger men and do an adequate or better than adequate job then for me it's expected that he performs like a middle of the road player.
I'll be more concerned come February, March if he continues to play this poorly. Then I'll feel that he really hasn't progressed but rather regressed as a sophmore.