He obviously has problems with rebounding and defense, that was understood on draft night but he has yet to really work with a NBA strength and conditioning program so this isn't really the best time to be judging him on those things.
A number of points here:
1) first of all the above is not really true. NONE of these kids has worked with NBA strength and conditioning programs. Some of them are nonetheless able to board/defend. That Hawes does not, compared to his peers at the same point in their careers, is quite significant. they will get better too at the same time he does.
2) and in addition, as the son of an NBAer, a guy who has obviosuly developed very sophisticated post moves and whatnot through extensive coaching, and has been ont eh edges of the NBA world since birth, I would say its far MORE likely that Hawes has exposed to that sort of program than soem raw kid out of Africa or whatnot. That goes for all that plyometics stuff too. That's hardly cutting edge, and any top athlete knows about it. One who has trqained his whole life for the role is quite likely to already be using it to some degree too.
3) I am actually a bit nonplussed about it to some degree, as Hawes is more mobile than advertised, and has good length. Physically, he should be able to do better. At a certain point it comes down to mentality/knack. Just as some people see the game as scorers, some see it as rebounders/defenders (see Justin for example). Switch the two guys from body to body and I suspect they largely switch roles (although Justin would probably have a hard time staying in the NBA in Hawes' body).
4) Hawes absolutely needs to get stronger. Randolph Morris, who is maybe a year older and a fringe NBAer at best just put his shoulder into him and bulldozed him wherever he wanted to go. But I would be a bit nervous about Spenser bulking up. He is already a shaky athlete. If he threw on 20lbs to bang with, it could tip the scales toward bad. Might make him settle into the post more though.
5) which brings me to a point which may sound unfair, actually two of them:
First, I think Hawes may actually suffer from having TOO many skills on offense. Or too many things he can do to some degree, but not dominantly. Sounds odd, but watching him attack it seems like he has a shot for every occasion form wherever on the floor. That should be a good thing, is a good thing in a lot of ways, but it actually impresses me that maybe its not. He ends up taking the first shot in his repertoire from wherever, rather than working to get to his spot on the floor, a prime spot. Would almost be better if he did not feel comfortable from everywhere so he would be induced to go where he has the biggest advantage. Hence if he gained weight, might almost help him to get dedicated to the post. In any case, looking forward, I could see this being perhaps the area of greatest growth for him. Simply learning how to use it, how to organize his attack. Rather than taking first shot, how to use one set of skills against the big slow guys, another against smaller guys. Again, properly organized and used, versatility like his is a huge plus and something many stars have. Right now, first impression is that its almost too much.
6) Second point though, and a little counter to that last, is I wonder about Hawes' upside compared to almost any other kid his age. Here's why: he has all the skills already. Normally when you talk about upside for a kid its in anticipation that he will develop skills to go with an already impressive physical package. Give him a few years, let him work on his jumper/post moves or whatever, and start dreaming. But Spenser already has all of that. And I do mean almost all of it. Jumpers, post moves, can handle, can pass. His skills are already complete. As always can refine or whatnot, but other than adding a three point shot (which I would rather he did NOT) he's already got almost everything you could learn in a gym anyway (and no doubt through endless work in a gym, probably playing against his dad since about age 5 -- just guessing). So the whole potential thing is twisted.