The huge problem here for Canelo is the same thing that was a problem for all of Marciano's opponents: Marciano had a limitless gas tank and could seemingly increase his workrate at will to a crazy tempo even late into the fight. It's doubly bad for canelo because he himself has never had the best gas tank. Skillswise ginger is way ahead but this is a case where raw physicality and guts blasts through the more talented fighter and sends him to the infirmary. Marciano KO win.