Floyd Mayweather defends upcoming fight against Andre Berto

Los Angeles: Floyd Mayweather's latest title defense began outside the ring on Thursday as he fought to validate his upcoming bout against Andre Berto.

Mayweather, coming off his victory over Manny Pacquiao in May, is gearing up for what he says will be the final fight of his career on Sept. 12 at the MGM Grand in Las Vegas.

Victory would take him to 49-0 and match the record of former heavyweight great Rocky Marciano, though Mayweather has been criticised for choosing what many consider an easy opponent for his swan song.

"I hear I've been getting backlash. I chose Berto because he's exciting," Mayweather told reporters from his podium.

"The difference between Berto and Pacquiao is you guys put all the hype in Manny. But this fight is a very intriguing matchup."

The fight is a far cry from Mayweather's 'mega-fight' clash with Pacquiao, which took five years to finalise and became the richest bout in boxing.

There was less fanfare on Thursday with both Mayweather and Berto in casual dress and flanked by the boxers confirmed for the undercard while the 38-year-old Mayweather took time out to pose for photos with fans.

The 31-year-old Berto, who has known Mayweather since he was a amateur, has a 30-3 record and is a two-time welterweight world titleholder, but is just 3-3 in his past six bouts.

Despite the impressions that Mayweather ignored several more qualified boxers, Berto promised if the fight does not deliver a good show he would not be to blame.

"Have you ever seen a boring Andre Berto fight? Everyone needs to question Floyd," Berto said in relation to reaction from the outcome of the clash with Pacquiao where Mayweather was criticized for being too defensive and the fight failed to live up to expectations.

"Every time I fight it's exciting. Every time Pacquiao fights it's exciting. There's one common denominator that's making it (boring)."

For his part, Mayweather does not seem fazed by the muted interest in the fight.

"No one is forced to buy this fight," Mayweather added.

"Andre Berto is going to push Floyd Mayweather to the limit. That's one thing I do know."