The kid is 17, and I reiterate he's a kid. Unless he's done growing, the odds are pretty low that he has an NBA body now. Now I think there is room for discussion if he has an NBA game now -- and we shall see this year.
Personally, I think he's leagues ahead of the project big men that we have added to our team the past decade, but he still may struggle against SEC bigs. He will probably struggle in rebounding initially. The hope is that his skill facing the basket and foot work will let him overcome his lack of bulk -- it's tough to compete under the boards against someone with the same height but with an additional 25-30 lbs of muscle.