No disrespect Makk but your way off on this conditioning shit. There are plenty of fighters who look out of shape, and are rarely cut, who have the best stamina in the game.
What happened in this fight is that, although it appeared Diaz was doing his thing in the early rounds, Marquez was actually landing the cleaner and harder shots, which eventually took there toll.
BTW, to anyone who referenced Harold Ledermans scorecard, never pay attention to Lederman in fights like this. Actually, you have to take most of his scores with a grain of salt. He favors aggressors, and even if, in a fight like this for example, the guy who is backing up is actually doing more damage, he will always pick the guy who is coming forward and is too biased towards that style.