Future and past at play in Floyd Mayweather’s bout with Andre Berto

He’s promising a career closing that few believe is coming, selling a fight many have expressed disappointment and disinterest in.

But Floyd Mayweather Jr. (48-0) says he knows boxing fans, and he predicts, “They always tune in. They say one thing and do another.”

Mayweather, 38, appeared Thursday at the J.W. Marriott at L.A. Live to promote his Sept. 12 welterweight title fight against Andre Berto (30-3, 23 knockouts), and said he plans for the pay-per-view bout at MGM Grand to be his last.

“They said they’ll offer me a lot of money. … I’m OK,” Mayweather said. “I’m an old man now.”

Mayweather’s father, Floyd Sr., expressed doubt that his son will retire, but declined to elaborate.

And Mayweather Jr. could barely contain a smile about the new Las Vegas arena being built for an NHL team that is to open next spring.

“They say [it’s] the arena that Mayweather built,” he said. “As of right now, I’m only focused on Sept. 12. I’m comfortable. I’m happy.”

First, he has some audience building work to do for the Berto bout.

“Berto … he’s always in an exciting fight. If he gets knocked down, always getting back up. Fast hands. Good boxer. Eighty percent or better knockout ratio, and did the same thing [Saul] ‘Canelo’ [Alvarez] did against Josesito Lopez, stopped him,” Mayweather said. “It’s all about entertainment.”

Berto missed at least three past opportunities to land a Mayweather fight, with two of the chances slipping away in defeats to Victor Ortiz and Robert Guerrero.

“I see Floyd at ringside [versus Ortiz] and lose … these are people I should’ve beat,” Berto said. “Ain’t nobody can’t tell me what I can’t overcome.”

Now 31, two years removed from a career-threatening right shoulder injury, Berto alluded to major upsets in the sport’s past -- Buster Douglas’ knockout of Mike Tyson came up -- and he pointed to how the timing is better now to take on the unbeaten Mayweather, who earned more than $220 million for his victory in May over Manny Pacquiao.

“An athlete knows himself to a T, ” said Berto, who is trained by unbeaten Andre Ward’s trainer, Virgil Hunter, and is engaged in notorious BALCO figure Victor Conte’s speed-endurance high-altitude conditioning program.

“I know what shape I’m supposed to be in, that I’m punching hard. I’m going to come in there feeling strong, fast. You’re going to see a kid in there that’s been at the high road, that’s had his falls, and is now back ready to make it happen. There may be a fairy tale end to this situation.”

Mayweather said he has his own plans, to match late heavyweight champion Rocky Marciano’s 49-0 record at retirement, to close a run that has included victories over future Hall of Fame fighters Pacquiao, Miguel Cotto, Juan Manuel Marquez and Oscar De La Hoya, and to head toward a life with his children, promoting young fighters and driving his lavish sports cars.

One of the cars has a $160,000 price tag -- for service, Mayweather revealed.

A 40-to-1 favorite, Mayweather agreed the bout lends itself to the possible career exclamation point of a knockout victory.

“With the way he comes and the way I’m going to come -- if there’s not a knockout, there’s going to be some knockdowns,” Mayweather said. “And there’s going to be blood.

“They say I’m training a lot harder this fight. Just want to go out with a bang, I guess.”

Berto suggested boxing fans who’ve roundly criticized Mayweather’s opponent choice are still chafing over the disappointing action in Mayweather’s May 2 unanimous-decision victory against Pacquiao.

“Have you ever seen a boring Andre Berto fight? No,” Berto answered. “Everybody needs to question Floyd. Everybody’s upset Floyd-Pacquiao was boring. ... Y’all can’t take it out on his opponent. There’s one denominator that’s making it a problem. You can’t come at me … every time I fight, you know what it is.

“Everybody’s still bitter over the Pacquiao fight. I don’t blame ‘em. I’m a fight fan myself.”

Mayweather responded, “He’s fighting a boring fighter ... and getting his biggest payday.”