Depends on the case. Duran, for most of his career, didn't take training very seriously even before he moved up to Welterweight. Now, Mayweather is no Sugar Ray Leonard, but he is one of the most well-conditioned boxers in the history of the sport and one of the smartest as well. Now, if it's the Duran who came in dehydrated and out of shape in the rematch("No Mas") against Leonard, I'd say Mayweather would win by close UD. If it was Duran at his absolute best shape in his career who handed SRL his very first loss, I'd say Duran would figure a way to get past the shoulder roll and slow Mayweather(while Mayweather still wins a couple of rounds with his defense and wit) down and win the big rounds. Duran by UD

Duran

Duran at 135 easily

At lightweight Duran stops Mayweather in less than 10 rounds. At welter I still give Duran the advantage but it could go either way.

Duran destroys Floyd. We saw how Floyd reacted when he got tagged by Shane Mosley and Miguel Cotto, and Duran is more powerful and much more vicious than any of these guys.

Duran would knock him out at any weight under welterweight between rounds 6-8.

At 147, or higher Duran would get a easy UD, or a mid to late TKO.

I think Floyd will win by decision because Duran is a brawler and Floyd is a counterpuncher. His ability to adjust will get him the victory.

Duran. Monkey Mayweather is overrated.

Mayweather

At 135....IT's always Duran..............the upper weights it's no so easy.