Heading into the much hyped 'Fight of the Century', Floyd Mayweather Jr. repeatedly said his welterweight showdown with Manny Pacquiao was all about defining his legacy while preserving a perfect record as a professional.

In many ways, it was a case of 'job done' on Saturday night at the MGM Grand Garden Arena where the 38-year-old once again showcased his brilliant defensive skills as he won a unanimous decision over Pacquiao in their title bout.

Mayweather, a polarizing figure because of his arrogance and flamboyant showmanship, improved his career record to 48-0 and said during the post-fight news conference that he would fight once more, in September, before retiring from the sport.

Golden Boy Promotions President Oscar De La Hoya, who was beaten by both Mayweather and Pacquiao before calling time on his own glittering career, was distinctly underwhelmed by Saturday's fight - mainly because of Mayweather's style.

"Sorry boxing fans. Call me old school but I like the fans getting their money's worth by watching an action-packed fight," De La Hoya tweeted after what is expected to be the top grossing prize fight of all-time.

"I'm just not into the boxing, running style. I like jumping out of my seat because a fight was exciting and the fans got their money's worth."

Former heavyweight champion Mike Tyson agreed, tweeting: "We waited 5 years for that... #underwhelmed".

The fact that it took more than five years to make the fight happen was also part of the problem. Granted, Mayweather and Pacquiao are the greatest boxers of their generation but, at the respective ages of 38 and 36, they are in the twilight of their careers and most pundits believe they have lost some of their skills in the ring.