Diaz has a granite chin, his head snaps back and he doesn't even step away. As tough as they come, he takes 3 solid shots in a row and he's unfazed.
A good chin, but I wouldn't say granite based on the strikes he ate in that sequence. The head kick that Condit hit him with landed with the foot, and pretty close to the toes at that. It's not fun to get hit by that, but it doesn't do nearly as much damage as a clean shin bone to head hit such as the one he landed on GSP.