Brooks was incapable of setting up the rotations correctly. He didn't play his starting center, Krstic, enough minutes. He played Green way too many minutes and most of those he was out of position.
Had Brooks gone with something like this from his SF/PF/C position, Presti wouldn't have felt the need to make the trade:
C - Krstic 32/Ibaka 8/Nazr, Collison, or one of the young guys the rest
PF - Ibaka 24/Green 14/Collison 10
SF - Durant 38/Green 10
I'll go out on a limb here and say that Brooks didn't play Krsitic for 32 minutes while limiting Green to 24 and Collison to 18 mostly because he wanted to win some games, maybe.
Green has never been that good. To win games, his minutes need to be reduced. And Collison played 21.5 minutes that season (in the playoffs he was 24.5). I actually reduced his minutes (which were less than 18 as I figured Nazr & the young guys would have picked up at least a couple minutes a game at center). I bumped Ibaka up 5 and Krstic up 10 minutes a game, which is what reduced Green's minutes. Krstic was a much better rebounder and much more efficient player than Green was. He should have been playing more minutes than him. You see, the whole problem with OKC that year was Brooks, and frankly it is still their problem. Brooks quite simply isn't a very good coach.
As bad as you may think Green was at that point, he was still exponentially better than the Krstic OKC got.
Per 36 numbers for 10-11 OKC stats
Krstic - 12.6 p, 7.3 r, .7 a, .6 s, .6 b, 1.2 t, 3.8 f - 49.8% FG, 80.3% FT
not a whole lot different than Green
Green - 14.8 p, 5.4 r, 1.8 a, .8 s, .4 b, 1.5 t, 2.8 f - 43.7% FG, 30.4% 3PT, 81.8% FT
I mean the simple truth is, Brooks played Green far too many minutes and did so at a position that wasn't nearly as conducive to winning.