The other thing about a fighter like Diaz is he knows damn well going in that he's going to have to absorb wild amounts of punishment, especially against a fighter like Manny. I'm not trying to say Oscar and Hatton weren't ready to fight, but there was a part of them that had to be shocked sh*tless at what was happening to them. When it happened to Diaz, he was more mentally prepared for it.
Diaz has an excellent chin and he actually put his damn gloves up. Man, he took a beating but that fight should of been stopped earlier!
He had heart and will, he was very hungry to win that fight. heck anyone would want to win against Pac.
He may have taken more punishment getting the belt than losing it. Even days after that fight, it looked like Morales had taken chunks of Diaz home with him. There's no way Oscar would be willing to take that kind of damage, even with all that wanting to be KOd, so he could 'go out on his shield' nonsense, deluding himself into thinking that'd get him acclaim in Mexico (and that he was capable of subjecting himself to that experience). Another part of the different mindset that's better (healthier, too) is that Diaz was genuinely thrilled to be in the same ring as Pac; seemed like he would have taken the fight for table scraps.