The Spurs have never developed a big man. The team will spend time and energy on developing their wings, bring in a shot tutor, but there's never been a single coach on this staff (to the best of my memory) who has known how to play as a true 'big' or to teach those skills.
If you don't come to the team with a major skill set, then you're not going to get better being on the Spurs. Marc Gasol had his brother Pau to work with, I wonder how much time Tiago gets with anyone who can help him get better, I'm sure Chip works on his free throws, but what about his post moves,what about his rebounding techniques, is he going to learn from Bonner???? or Blair???
Spurs should send him to a big man camp or have him work with the Dream in Houston.
Since you can't fix stupid, at least you should be able to prosecute it!