Why? He's had years in the system. You can't expect a player to be perfect in 2 minutes every 15 games or in the one game with decent minutes a year. Rookies make mistakes no matter how hard they work in practice.
You cannot really evaluate a player on this basis or the evidence shown from it, either. I'm not even sure why the Spurs would feel compelled to in Ian's case.
Uh, he's shown flashes against NBA teams. The Nets are terrible, but they're better than the D-League talent he consistently wrecked on during his Toros stints.
Blair, the 37th pick (Mahinmi is the 28th and has years in the Spurs system and is exactly what we need at C if he could play even average) has gotten minutes from the very beginning. Mahinmi hasn't even been considered. That's discounting all the $$ the Spurs have invested into what they've deemed a bust without any game evidence.
I don't think your arguments hold much water. They're only your opinions, not really arguments - how can you know Mahinmi's BBIQ with very little hard data available, or read the coaches' minds and know why they aren't playing him? The only way to base any real argument is seeing him get some consistent time in real NBA contests and studying both his play and Pop's reactions.
I don't know what could be hurt with him playing, especially when he played well against the Nets. He's exactly the skillset we need at the 5 and in case you forgot, we won a le with Nazr Mohammed in the middle. Don't forget we acquired Nazr mid season, either, and from the Knicks no less.