Yeah, but... BOOM! This content is protected To be fair, the same goes for most opponents at that level. The better fighters you face, the less potent some of your best punches become.
Thats pretty standard procedure though. Thats like saying the higher the skill level a fighter has gone up, the more a punchers KO percentage has gone down. Its clearly going to happen.
He lost his power when he moved up past 140. He was a lot bigger than his opponents as a JWW. At WW, the only good opponent he overpowered was Zab. And everybody overpowers him. Cotto ain't a juggernaut beyond 140. His opponents had sumthin to do with it too, but it's mostly the weight.
Although I wouldn't go so far as to say everyone overpowers him, I do agree that it is the weight(opponent)that has affected his power shot. It hasn't really carried up all as well as he might have hoped.