Wow, I thought most people who have played would view it in the same way that I have... He's kind of getting shafted and is being forced to take a backseat to McBob, and as a result, he feels lost and rushed when he does get out on the floor.
In my experience playing, coming off the bench was extremely difficult at first, because you don't know when coach is gonna pull you, so you're trying to make something happen quickly, which often doesn't turn out well. It's hard to play your game though when you don't know how long you'll be out there. It affects everything... Your shot, your passes, your approach... EVERYTHING - until you grow to understand what is expected of you in that role and become accustomed to doing it in the minutes you expect to get.
Additionally, some of the foul calls he's been getting are complete BS... I've seen him rack up a million fouls on setting screens that he didn't deserve.
I think he is having a hard time getting into the flow of the game coming off of the bench... And IMO, as our #1 pick, he should be starting and playing a lot more minutes than McBob. When he starts feeling more comfortable in his role, he'll be back to doing the stuff you saw in summer league.