You missed games played. He got unmercifully put on the shelf for the remainder of the season in favor of Jarron Collins his rookie year and he was playing well. Pretty sure that broke him for the next 3 years.
Koufos has/had too many good things going for him to totally derail him because of mistakes of pure inexperience. He's not a world beater and no one said he was either, but there's infinite room in the NBA for 7-footers with no real weakness to their game (even if lacking obvious strengths).