I don't think anyone but Wemby and Fox have locked down start spots right now. If it was up to me, I'm staring Wemby, Barnes, Harper, Castle, and Fox. This might change after we see what moves the Spurs make, but I think people here are 1) overrating Castle and underrating Harper currently. Don't get me wrong, I like Castle a lot, but he has a LONG way to go before he's an all star. Obviously, so does the guy who hasn't played a single game in the NBA, but if you were forcing me to pick one of the two that is more likely to be be a #2 caliber star, I am going with Harper.
That being said, if you're also asking me who's the most likely to come off the bench given the history of this coaching staff and organization then I definitely believe that Harper is most likely to start the year coming off the bench. But I also expect him to just be too good for that. Maybe the evaluation changes once we actually see him against NBA compe ion, but I have a hard time believing Devin is going to be the best contributor out of him, Castle, and Harper and warrant starting.