Watch the Cotto-Mosley fight. Cotto was punching off his back foot against Margarito still landed harder shots, but he was beating Margarito up mentally, he wasn't stopping Margarito from landing punches, and he wasn't tiring Margarito out.

Want another example like this
MAyweather-Corrales vs Corrales-Castillo: Castillo landed probably 3x as many punches against Corrales, because Corrales was able to find Castillo it changes your mindset in there. Being able to hit your opponent makes you tougher, it your strength doesn't get sapped as much knowing the other guy is going through what you are. That's why Holyfield could survive against bigger heavyweights, thats why Leonard survived against Duran in their first fight.