You're more worried about defensive rebounding against the Spurs than the Thunder? Thunder were one of the best offensive rebounding teams in the league, and better than San Antonio. Aldridge gets 10 rebounds per 36 minutes. Aminu and Meyers got 9.6 rebounds per 36 minutes. Aminu has done a good job of holding him off the boards in the past. Worrying about Aldridge rebounding and thinking that they'd be favored without HCA because of that is a stretch to say the least.
That 13 & 10 would get replaced by committee. It's not like it vanishes into thin air.
Thing is, he's probably going to play, and you said they'd be favored even if he did. Which makes no sense.