the fact the question is who would win between a welterweight and the middleweight champ tells me the welterweight is highly regarded.
Martinez is too powerful for Mayweather. This fight will not happen. Floyd is technically superior but he's going to get hurt badly here, hence, he will fight those who are coming up frrom the smaller weight-classes instead.
Barker is a MW - and though he did do an excellent job of absorbing much of Martinez' offensive output, he was still occasionally getting hit with some good clean punches and able to successfully absorb them (until the end of course.) Mayweather is a WW - and so the more pertinent question, in my mind at least, is whether or not his punch resistance will be able to hold up against the bigger man when Martinez inevitably lands his occasional power shots. I have my doubts.
If Mayweather could make middleweight, he'd get an easy victory over Martinez. Martinez has a style very much like Froch, carrying his hands at his waist. Mayweather would eat that style alive. If Mayweather's speed and power carry up to MW, I see Martinez tasting canvas at least twice in a matchup.
You're crazy, Sergio will punch right through Floyd's one dimensional, doesn't move his head, come foward attack. This isn't Sharmba Mitchell. This is a big, solid 154 fighter with greater reach, who's just as fast, and is very skilled despite being somewhat of a wild gunslinger. Sergio will hit Floyd with combinations that start from the bottom or the top, and Floyd won't be able to block them or get out the way fast enough. This isn't a 6 foot middleweight that we're talking about. We're talking about a guy that doesn't appear to be able to move backwards as fast as Sergio moves foward. Perhaps Floyd was rusty in his last fight, but either way, this is no walk in the park and I wouldn't bet on Floyd to win. I think his reign as this unbeatable fighter is coming to an end. His layoffs may have caught up to him.
Here is the situation... Due to Barker's stance, gameplan, style, and defensive ability, plus in a SIGNIFICANTLY large part, due to his SIZE, REACH, and HEIGHT, he was able to stand back at a "relatively" safe distance and force Sergio to extend himself to hit BARKER. Even with a significant enough size advantage and relatively high boxing acumen in the sense that he used the right game plan even if he wasn't good enough to implement it, Sergio STILL MANAGED to pierce through his guard and land punches. Barker; however, PHYSICALLY COULD land on Sergio without Sergio landing on him because he had a significant advantage in reach, height, etc... BUT... Sergio's counterpunching ability, speed, and determination put Barker in a position where he was getting hit DESPITE this. Floyd is the SMALLER MAN. He doesn't share the same characteristics that Barker does, nor will he posess the same types of potential advantages. In addition, Floyd was hesitant to stand in Ortiz' kitchen which contributed to him missing many punches, plus throwing his punches short and putting himself in a position where he could get timed and countered. I don't know what you all think, but Martinez has EXCELLENT COUNTERPUNCHING ability, AMONG THE BEST IN THE SPORT WITH SOME OF THE FASTEST HANDS. Mayweather will have to FORCE the action, get inside of Martinez reach, which will put him at signficant disadvantage. And for those of you who think Mayweather can just simply walk foward with his hands up in his one dimensional attack, you must realize that it probably won't work against Martinez who's too intelligent and will adjust accordingly as he did against a MUCH BIGGER MAN than FLOYD and still managed to KNOCK HIM OUT WITH ONE PUNCH. Perhaps if Floyd approached Martinez with the same style that Bradley used against Alexander, he would have a better chance. But Mayweather is NOT BRADLEY. Mayweather's best chance in this fight would be to "RUN" and make Martinez the aggressor and chase him. Even then, it's too dangerous a fight for Floyd. He's TOO SMALL. Ya'll are delusional.