Playing a rotation like this in back to back games is not about chemistry. That is a Pop apologist cop out. The Thunder are an athletic team...and you have an athletic big on the bench that knows the system and played pretty well against another NBA rotation big just a couple of games ago. You also have another young, athletic player that is a good defender that knows the system very well. Oh, and there is that veteran big you signed because the team needed shot blocking(as TJastal pointed out, we gave up 54 points in the paint).
Would Mahinmi, Hairston or Ratliff made a difference? I think they could have. At the very least Hairston could play 10 minutes while Parker got a little bit more rest and Hill ran the point. Ratliff or Mahinmi could have given Blair a few extra minutes on the bench that might have kept him from picking up that extra foul so he could be in there at the end of the game. A better case scenario suggests that one of those two could have blocked a shot or two in the third quarter that led to a fast break and an easy bucket....or Hairston, who is very good at blocking jump shooters, could have made a great defensive play on Durant. Things like that tend to change momentum, so maybe the run the Thunder went on gets shortened and the Spurs don't have to worry about overtime.
Though these scenarios are hypothetical, they are all plausible. Would they have happened for sure? Maybe not. But in a game like this there is no good reason not to test them, as all three players have the potential to execute them.