Ahhh... That is the $64,000 question for McCallum. We don't really know the answer yet. Pessimists believe he isn't, and optimists believe he is. We shall see... I hope he is. I hope he is good enough to eventually become Tony's replacement. Now, that would be a coup. If Jimmer also proves better than Cojo, that would be a real coup. (I think all Jimmer really needs to do is knock down treys at a Marco clip.) In the evolving NBA of "position-less" ball, they might end up playing beside one another instead of really competing directly with one another for PT.
I think Simmons is the real key here. I hope he will be such a great Manu apprentice that he, like Manu in his prime, will move from 1 to 2 to 3 as game situations dictate. We already saw some of this in SL, when Becky used him as the principal ball-handler to close the last couple of games. He shows signs of being a very good defender, also. Playing along side either McCallum or Simmons, if Jimmer's D could be counted on to be as good (?) as Tony's or Marco's, then he could stick and eventually get Marco level minutes.

McCallum isn't even close to Joseph as a player, and I'm not even a Cojo fan..