If the fight is at 154, Martinez by clear UD, but I can't see Floyd ever taking this fight unless he loses his 0 and realises his legacy is then dependent on challenges he takes.
Up to now no one has realy beaten Floyd Mayweather Jr. A few boxers have had some degree of short term secuess though. I see no reason not to pick Mayweather by decision. That being said Serigo Martinez may be the ideal guy to beat him. Martinez is an exlent boxer who is tall with a reach advantage over Mayweather. He is also a southpaw. Even though Mayweather has had past secuess against southpaws they give any orthdox boxer problems. At 154 I don't see Mayweather having that much power so I think this goes all 12 rounds. I thin Mayweather wins 7 or 8 rounds in a decision victory.
There is a good chance this fight will not happen, but also I don't agree that it has no chance of happening. Martinez just beat Pavlik, Pavlik was/is a big name. Fingers crossed.
Either Martinez or Williams at 154. I might take him against Martinez but Williams will pound and beat his ass.
I would take a Mayweather UD. Martinez still gets hit to easily and Martinez will be the one chasing floyd not the other way round.