The problem for Cotto is he doens't know how to fight off the back foot at all. Manny caught him repeatedly by moving backwards then coming in quickly and Cotto can't get out of the way. Mayweather on the oher hand is far more mobile, and when he moves out of Cotto range he will counter over count, around, underneath and Cotto won't be able to react quick enough. To make matters worse, Cotto doesn't actually have a huge arsenal of punches that will really hurt Mayweather, it's basically his left hook to the head or body, and like Oscar we might never see him land a solid one. I think mayweather has also stiffened up his jab a lot since then, and he has better learned how to stand his ground and comit more to the right hand. All in all Cotto could present some interesting challenges, but he will be a little too slow, and just technically outmatched like everyone else because they look for the wrong stuff to beat maweather.