In under 3 rounds? I would bet all my worth that GSP doesn't finish Diaz. Not in a million years.
He brutalized Condit and Diaz has 3 shit things going against him, A) he isn't nearly as strong, B) he has shit loads of scar tissue and C) he ignores that voice in the back of peoples head that says don't let that guy hit you in the face. Diaz has shit wrestling which means he is gonna end up on his back and he keeps a loose guard with almost no weight being given to maintaining control. He is gonna get brutalized worse than we have ever seen GSP beat anybody.