Miguel Cotto
Paul Williams
Antonio Margarito
Shane Mosley
Kermit Cintron
Joshua Clottey
Oscar de la hoya
Juan Diaz (Mayweather hinted he would go down in weight after his "vacation."
Cotto has a good chance, IMO, because of his strength and tenacity, his ring generalship, and his heart. Mayweather could, and most likely would, pick him apart, though.
Williams. No.
Margarito. Bigger no.
Shane...2 years ago, absolutely. Now...it'd take all of the cards to fall right for him, and a bit of luck. I just think Mayweather would outwork him and outpoint him.
Cintron could do 'ok' for the first 2-3 rounds, then I could see a KO by Floyd.
Clottey, if I'm Mayweather, intrigues me. He's raw, and young, but I would never underestimate this kid. He seems like he could definately make a run up the ladder to the top, IMO.
De La Hoya...he tried to bully Floyd in the first fight; that didn't work. Oscar is a skilled boxer; he should box Floyd. Trying to use his size and strength didn't work, so let him come to you.
Diaz...if Floyd moved down, this could be a very interesting fight. I think Diaz is a superb fighter, and is in his absolute prime right now, and will be for the next few (at least) years. Now is the time to do it (if you're Diaz).