I'm not so sure that OKC is a horrible matchup for us. I think that slowing down the game in half court sets can sap plenty of their youth and athleticism edge. Experience and savvy might matter more.
After all, wasn't everybody saying that Dirk, Marion, Kidd, and Terry were too old to compete with OKC? The age gap there might be even bigger. They had Chandler too (still not that young) but we have Rondo and Bradley. If Dallas can do it, we can too.
And wouldn't Rondo and Bradley end up on Westbrook and Harden? Not a huge athleticism edge for either team. I think KG would have some tricks for Ibaka. Durant would be the worry, but that would be true for any team. And he'd struggle to guard Pierce on the other end.
If they want to give Perkins heavy minutes, more power to them. He drags down their offense.
Bring on OKC, the more I think about it. It's everyone else (Spurs, Lakers, Grizzlies even) that would worry me.