Then a lithe Ukrainian-American dancer in a black tank top enters the studio, and Mayweather tosses the rope aside with a sly grin.
Seconds later, they're doing the jive. Mayweather caps the routine by flinging Karina Smirnoff between his legs and back out again with a bit more enthusiasm than grace - but he's working on it.
"Showtime, we're gonna put the sparkle on it," he says.
Boxing history is being made in this quiet studio in a corner of a strip mall in Las Vegas' endless southwest suburbs. For four hours a day, four days a week, Mayweather is preparing not to be his sport's pound-for-pound champion, but the best amateur celebrity dancer on a television reality show.
"I'm the only athlete that's active in his field and competing with two big challenges," Mayweather says, nearly bouncing off the mirrored walls with energy between routines. "I'm trying to make the impossible possible. It's about pushing myself to the limit. That sums it up. That's what I'm going into."
While Mayweather prepares to risk his WBC welterweight title on Dec. 8 in a fight with England's unbeaten Ricky Hatton, Mayweather is simultaneously competing every week on ABC's Dancing With the Stars.
His demanding workout schedule has ballooned to almost 12 hours every day, and he also makes weekly trips to Los Angeles for show tapings, leaving Sunday afternoons and coming back Tuesday nights.
So why would Mayweather subject himself to this? He acknowledges it's a bald-faced grab for fame, publicity and better pay-per-view sales - and with Oscar De La Hoya vanquished, he certainly needs a new white whale.
Though he isn't sure he has a chance to win the dance contest, Mayweather is confident he'll keep his belt away from Hatton. It's just that his celebrity hasn't gotten big enough for his outlandish tastes, even after defeating De La Hoya in May to remain unbeaten.
"It's just smart business," Mayweather says, sweating lightly while predicting he can convert more than 2 million dancing fans into pay-per-view buyers. "I think it's actually better for me, because it keeps me around positive people and in a positive area. ... And I'm getting a lot of rest in between. If I'm working 12 hours, then I'm sleeping 12 hours."
Mayweather can't stop moving even when he isn't dancing. With a video camera recording his every move in a room lined floor-to-ceiling with mirrors, the Pretty Boy is in paradise - and he boasts of everything from his jump-roping skill to his promotion company's prowess.
When the music starts up, Mayweather drops into the same expressionless concentration his boxing opponents have come to fear. Spinning, sliding, clicking his heels and flinging Smirnoff around the room with brute grace, he appears easily competent and possibly gifted - and Smirnoff reveals just how gifted when they take a break.
"He just learned that routine in 20 minutes," she says. "He's kind of messing around for two days, and then when I'm about ready to have a heart attack, he learns it in 20 minutes. He's not an easy student, but he's a quick learner."
Leonard Ellerbe, Mayweather's top adviser, subscribes to the theory that Dancing With the Stars is a form of cross-training that could bring out the best in his fighter, both mentally and physically.
"You can see how hard he's working to be the best at this dancing, and that carries over," Ellerbe says while watching his young boss spin Smirnoff. "Bottom line, all Floyd has to do is be in shape. He don't cut no corners."
Mayweather acknowledges he doesn't truly think he'll win the show, citing other contestants' apparent years of dance training.
"I was born at night, but not last night," Mayweather says. "They can't run game on me. I know who the professional dancers are, but it's still good for me to push myself to the limit. It really don't matter how far I get."