I would go with Mayweather by very close decision or maybe a drawish fight. Sergio Martinez is extremely dangerous for Mayweather and I would consider it his biggest risk to date. Mad props to Floyd if he takes this fight but I doubt he will.
He can also add a trinket at 160. I think this is actually a fight that can be made and would actually benefit PBF. He can say he has won titles from 130 to 160. And not just any. Its the lineal champion he would be fighting. I think this is where PBF would lose.
Martinez can easily be outboxed and countered and PBF has all the tools to do just that. He would nulify all of Martinez's offense and pick Martinez apart since he has terrible defensive fundamentals. It is too big a difference in class. I also see Martinez getting handled easily if there was a P-Will rematch, especially since I saw that P-Will did enough to win a 7 -5 decision against Martinez their first fight on 2 weeks notice *for Williams*
Sergio Martinez is an exlent boxer and a southpaw. In theory He should give Floyd Mayweather Jr. probblems. However Mayweather has been able to adapt to what ever he faces including southpaws. Mayweather 8-4 decision.
Martinez is athletic, but not an excellent boxer. He has God-awful technique and balance. He has terrible defense and a bad habit of lunging in with shots. I wouldn't be surprised if Floyd had multiple KDs in a fight against him.
It's not a bad habit of lunging in, that's him throwing his bodyweight into punches. If you notice he makes it a lot safer by fully utilizing the range and speed available to him.
Mayweather. I just feel Martinez stylistically isn't a bad match-up for him, he's not aggressive enough to make the extra weight pay, he's predictable in that he throws mainly lead lefts and right hooks (one shot that Mayweather has to look out for, could be difficult for him to see coming and it packs under-rated power I feel), nor do I feel he is quick enough to dart in and out against a guy with the speed, reactions and punch accuracy of Mayweather like he has done in recent fights.
Anyone who says Martinez is not a class boxer is deluded. Terrible defense my arse, having terrible defense against PW would leave you on clear street. He got KDed once FFS, one time... from 1200 punches. He lunges in because he's THAT fast, he can lunge in. Plus, it's all about addapting to the opposition. Slower and bigger opposition, some tactics, fast opposition, different tactics. Martinez on the top level, has faced slower opposition than him and he took advantage. Martinez faced the opposition from the bigger category. Against a smaller Floyd, he could just potshot from distance. Martinez can trouble Floyd with his jab. It's a close fight. And it speaks volume about Floyd, through the simple fact that Floyd has to look at a much bigger division to the one natural to him in order to get a decent challenge. As at WW... there simply isn't anyone, with Pacquiao... not wanting to take them tests.
Martinez troubles Floyd at first with all his movement and speed, but Martinez is there to be timed for Floyd. Mayweather's superior accuracy and timing combined with Martinez awkward balance is a recipe to rack up points via flash knockdowns. Floyd walks home with a UD. Martinez seems to have a great chin, and he's not aggressive enough to get knocked out by Floyd.
Sergio has great reflexes and speed but he isn't exactly technically sound by any means. He would eat counters comming in, would probably go down in the fight due to being off ballance which means Floyd wins a pretty comfortable UD.
Martinez looks really good against guys who have less than stellar defense. However, his own defense relies almost entirely on speed and reflexes. He had a huge speed advantage over Pavlik, and yet, Pavlik was able to time him and counter punch in 5 out of 12 rounds. Little Floyd may very well counter punch the **** of of Martinez in 8 or 9 rounds. I doubt if Floyd would play the fool, head hunt, and lunge in like Pavlik and Williams did. I can honestly see Floyd winning a decision in a fairly uneventful fight. A lot of that would depend on whether or not PBF could retain his speed at the higher weight. And for what it's worth, I honestly think that if he rematches Williams, Paul will beat him again. Only this time it would not be as close. If Pavlik exercises his rematch clause, and sticks to the damn fight plan, instead of constantly head hunting, he will probably knock Martinez out. I've watched Williams/Martinez and Pavlik/Martinez several times. The only reason Sergio finished on his feet either time was because both opponents got stuck on stupid and turned in rather poor performances.