LAS VEGAS » Floyd Mayweather Jr. insists this is it, though he may be one of only a few who really seem to believe it.

Nineteen years and 48 fights haven’t taken a big toll on Mayweather, but he’s not taking any chances. He has seen what taking too many punches did to his uncle, Roger, and is determined to leave boxing with his brain fully intact.

Rich beyond belief, Mayweather doesn’t need to fight anymore. And he says he’s comfortable walking away from the sport he began learning before he could even walk.

"Not gonna miss it at all," Mayweather said. "I feel like I’ve been dealt a royal flush."

Those not on the inside in the Mayweather camp scoff at the thought he will retire after facing Andre Berto on Saturday. They wonder how he can resist trying to break the late heavyweight champion Rocky Marciano’s perfect mark of 49-0 and — perhaps more importantly — resist the huge money another fight would bring.

Those who know him best say he means what he says, even though an earlier retirement ended after 21 months.

"Why can’t a man go out when he’s had an illustrious career, accomplished everything that he needs to accomplish and be done?" Mayweather confidante Leonard Ellerbe said. "And he’s done it his way."

Of that, there is little debate. Mayweather managed, in a career that dates to his pro debut in 1996, to reinvent himself several times and make more money than any fighter before him despite a defensive style that borders on boring in the ring.

He earned some $220 million in his last fight alone, a staggering figure that dwarfs all his other paydays. It happened because the desire to see him fight Manny Pacquiao was so frenzied that people paid up to $39,000 for ringside tickets and 4.6 million households bought the pay-per-view at the princely price of $99.95.

The frenzy has long passed, replaced by a sour taste most got from watching Mayweather methodically dispose of Pacquiao. There’s so little demand to see him fight Berto that tickets were both available and plentiful direct from the MGM Grand in almost every section of the hotel’s arena in the days leading up to the bout.

Part of that is the hangover from Pacquiao, though part of the blame has to go to Mayweather’s choice of an opponent. Berto may be a former champion, but he has lost three of his last six fights — two of them to fighters Mayweather beat easily — and is a lopsided 20-1 underdog in man-to-man betting.

To try and sell the fight to those at home for a suggested price of $74.95, Mayweather has played up Berto’s aggressive style and vowed to seek a knockout.

"Berto is not a pushover," Mayweather insisted. "No matter who I chose the media was going to have something to say; the critics were going to have something to say."

Mayweather weighed in Friday at 146 pounds, a pound beneath the limit, for the welterweight title fight. Berto was a pound lighter at 145.

The promotion for Berto has been so low key it almost seems as if the fight is an afterthought to Mayweather. He bristles when it is suggested that it takes a name opponent for him to sell a fight, especially when his last five fights on Showtime have closed in on 10 million pay-per-view buys with total revenue of nearly $750 million.

"Nobody’s forced to watch," Mayweather said. "Watch if you want to watch. If you don’t want to watch, don’t watch."

Berto says people should tune in, especially if they want to see Mayweather get beat. Though a huge underdog, he has never been afraid to trade punches, something opponents don’t normally do against Mayweather.

"I’ve been counted out from Day 1," said Berto, who represented Haiti in the 2004 Olympics. "I’m coming for my respect and for everything I deserve. He’s sharp but I have certain tools that will make things difficult for him."

If so, Berto will do something Pacquiao couldn’t do. Mayweather was at the top of his game when he beat his longtime rival in the richest fight ever, and if he does retire as planned it will be with a 49-0 record that matches Marciano.

And Mayweather made it clear he is serious about calling it a career.

"My health is more important," he said. "If you stick around anything too long, anything can happen. I’m not really worried about losing, but I want to have a sharp mind. You can make a lot of money, but you still want to be able to talk, walk, and have a sharp mind."