Also...
The Thunder were ranked third in the NBA for Defensive Efficiency (Pts Allowed per 100 Possessions).
Who are the top teams you might ask?
1) Indiana (Hibbert)
2) Memphis (Gasol)
3) OKC (Ibaka)
4) SA (Duncan)
5) CHI (Noah)
6) BOS (Garnett)
I think he's a better/more important defender than you give him credit for. Keep in mind that having an elite shot blocker changes the mentality of offensive players as well. In effort to not being stuffed, they tend to take outside shots/floaters which are in turn lower percentage shots.