Between Mosley, Floyd and Cotto. Mosley should be at the top of the list. has speed, chin and power. Hard to beat stylewise for pac. Mix feeling on floyd and cotto. But ill go with Floyd next. Has speed, less power of the other two. But his accuracy will make his punches just as bad. His chin is still a mistery for me, since it hard to hit him clean. Pac will surly give him a chin check. Cotto could punish and hurt manny more the floyd. Pac will be able to run away for the first half. I think pac can hurt cotto just as bad as he ice Hatton. Just a matter of who lands first.
Floyd without a doubt. Right-hand counters all day... I suggest you re-watch the Marquez fights.. esp. Marquez-Pacquiao II. Mosley is hit or miss at this point. Around 5-6 years ago... when he was in his prime & beat Oscar..., that Mosley beats Pacquiao @ 147 by late knockout after being down a round or two due to slow-starter syndrome & Pacquiao's everlasting work-rate! & Cotto can be dragged into a slug-fest... which he will lose (Pacquiao can take more punishment than Cotto... and out-lands Miguelito 2 to 1!). To win or even really push Pacquiao, Mosley & Cotto have gotta come in in their best form... whilst Floyd, he just has to do what he's done in all his fights... come in relaxed & pick Pacquiao off. Manny is still a sucker for a composed, great counter-puncher's right-hands (and there are only 2 of these in Pacquiao's weight ranges: Marquez & Floyd Mayweather Jr!). Hands down, it's Floyd Jr.
IMO, In order Cotto: Will/Would match Pacquaio in every quality. (He who takes it will win) Mosley: Bigger stronger version of the style that gives Pac fits. Floyd: Tough as in a beating, not in this fight. 12 rds (not interested)
Stylistically, Mosley is the hardest fight for Pac. Cotto is the easiest - though obviously not easy at all.
Mayweater simply Outboxes Manny. Mosley KO's PacMan. Cotto would be the most interesting - with a chance at Manny winning.
At this point, with SSM it depends on how he shows up. As an Old-timer rolling back the years... or as a genuinely old, lethargic fighter! The Mosley who beat De La Hoya KOs Pacquiao. Though, that same De La Hoya KOs Pacquiao as well!