He's clearly going for the ball. The contact to the head is clearly incidental. He's clearly trying to catch him on the way down. He's clearly trying to step away after the foul. OKC has several enforcers on the team who aren't good defenders. Nick Collison isn't one of them.
They've got to get a better handle on what is a flagrant foul in the playoffs. Even if you're setting a precedent for the series, this is a bad time to try it.