red, IQ effects almost everything (there are exceptions ... ft shooting, etc.)
He will be better as his iq improves. He won't be as good defensively as guy with the same iq and better def-related ratings. Also, his ath is pretty average as well. With low def, mediocre ath and iq I'd expect him to not be that good an interior defender right now.
FYI, he fouled out three times in your last 29 games.