Ofcourse he watches tapes. He also watched when JMM faught Juan Diaz and he knew JMM had trouble with another fighter that was moving up in weight. So there he knew it he probally wouldn't be much of a challenge and accepted the fight.
You never know Chavez was with Margarito after the Cotto fight maybe he gave him that tip. Chavez didn't want his son to fight with Camacho Jr. even though Camcho son stepped up to the ring and challenge Chavez Jr. I guess he might hate PuertoRicans.
If Marquez surprisingly does good, but loses it will only make you wonder if he could've pulled it off at 140 or 138. But the truth is Mayweather will win by a landslide. Marquez will start moving foward, but will back down just like he did in the Diaz fight only this time around he won't be able to comeback in the fight by hurting his adversary.
Floyd huggers say that, but it can also work the other way around. Manny lands so many punches that Mayweather will need add a third hand for his defense..
I wonder if instead of having more stamina he might get tired faster. After all he's been training for a longer period of time than he's use too. I think the extra training plus coming in leaner can be a problem, but only Cotto will know until fight time. same happen to De La Hoya he didn't really know until he stepped in the ring to perform and he just didn't have it. He fought way better against Mayweather, but against Pac he just looked weak.