David Diaz took the punches pretty well actually, was he on roids then? Oscar took them pretty well. Hatton was an anomaly compared to the rest of his career. And Cotto probably could have gone the distance, granted Pacquaio's power did look good in that fight. I don't remember him being close to stopping Cotto in the second though.

Also his KO rate has always been pretty damn good against guys not named JMM. After his "step up" against Ledwaba he had 11 KO's in 15 fights against good opp, the non KO's were Sanchez, first Morales, second Barrera and Larios. And honestly you can make reasonable excuses for some of those fights. Morales of that first fight was unlikely to be stopped by just about anybody, second Barrera fight he seemed content to cruise a lot more than usual, the Sanchez fight was just odd and dirty and ended early.

I actually would be more surprised if he hadn't been on something, he obviously looks like he's hiding something. But just saying, all the speculation outside of that can be argued against easily, the putting on weight thing is not that hard to counter and really so is the power thing. One punch power is far from the reason he stopped ODLH, it took 9 rounds of bludgeoning to stop David Diaz, he took out Hatton early but Hatton had just been badly hurt by Juan Lazcano and hurt by lesser punchers like Collazo, and Cotto never had the greatest chin and still could have finished the fight.