He's a really good defender, he has the capability to harass, pester and really cause problems for two positions at the next level (SG, PG). He's a good rebounder for his size. But, he lacks consistency with his overall jumpshot, and his passing needs improvement.
He isn't the type who can play spot point minutes either. Although, he has fair ball handling ability. Character wise, despite some minor past incidents, he's a good guy. I'd say he would be good D-League or overseas material. He could very well develop these other desired traits.
I.Q wise: By no means is he a genius, but he's not a rock or anything. The Spurs system may be a bit complex for him, but he picks things up with time.
Defending and rebounding come natural to him. I'd suggest simply improving offensively.