Also, there's no doubt that Noah is a very good rebounder at this point. However, is he an elite defender?
According to Basketball Prospectus, opposing players actually scored slightly above their averages (by 3.3%) against Noah. Also, the Bulls were better defensively when Noah was off the floor than when he was on. Even though I think it's clear that Noah is a pretty good defender, there's a question whether he's an elite, impactful one.
Quite honestly, I have no idea how good Noah's defense is, compared to the average defensive center. However, I don't think he's at the level where his defense single-handedly changes games the way that, say, Dwight Howard's would.