It's his D that's the issue.
That's the key. He seemed to have some Leon Powe in him offensively and on the boards (although nowhere near as polished), but, much like Leon when he got in the league, the defense is suspect. In order to make a team like this, with his skillset, he would need to be an elite defender, and from what I have seen, he is pretty average at best. Put him against actual NBA players, and I think the shine would come off pretty quickly.
Plus, there just is no room for him on this team. They have much more use for an extra wing than an extra big man at this point.