mayweather will never fight boxers like pacquiao or martinez, not anyone who has chance to beat him because is a coward and all his grandeur his built on the fact that he has no losses in his record.
The truth is that mayweather really lost one fight(mayweather vs castillo 1)and he suffer figther that are soutpow(zab judah almost won if he did not gassout in the second part of the fight) or fighther that pressure him for 12 rounds non stop(castillo) and both pacquiao and martinez are southpow and especially pacquiao could pressure him for 12 rounds non stop.
Remember that he retired once before because he he did not want to face margarito (a pressure fighter) and miguel cotto(at the time unbeaten and at the top of his game).
I am sure that now mayweather will try to fight cotto because is shot(he is not the same fighter after the margarito and pacquiao beating).
Do not get me wrong Mayweather has exceptional skill defensivly, really fast and accurate puncher, but he his a light puncher with frail hands and because of that he his not that all time great that most of the people think he his and if he ever lose once he would be exposed.
Mayweather miss the greatest attribute of the all time great boxers in history : THE BALLS. Because of that he will never be at the same level of DURAN, LEONARD, HEARNS or HAGLER, REAL MEN that did not fear to lose and got in the ring with the best at that time.
Oscar de hoya is much greater than mayweather because he fought everybody and lost to floyd in a split decision that could have gone eather way when he was at the end of his career and on his way down.