spurs don't play big 3 ball. If their offense starts clicking, it doesn't matter who is on the court. They roll.Lots of teams aren't disciplined and the Spurs don't beat themselves - the clippers and jazz do though. Also, you need a big who can guard Timmy one on one, and a pg who can guard Tony, and a combination that can play the PnR. If you have that, you can stay at home on shooters and not be forced to help. The Thunder have that and their big 3 is more explosive, more athletic, and more dangerous than the Spurs big 3.
Letting Duncan/Tony/Ginobli try to beat you and staying at home on everyone else would kill most teams because those 3 could beat you 4 games out of 7 - but they're not beating the big 3 of the Thunder and that's why this strategy works.
Okc isn't that kind of team.