Floyd Mayweather Jr., talked with Leonard Ellerbe (right), CEO of Mayweather Promotions, at one of Mayweather's workouts in Las Vegas, Nevada. (McKenna Ewen/The Washington Post)

When Floyd Mayweather looks to his corner Saturday night during his fight against Marcos Maidana, one familiar face will be absent. Since joining Mayweather’s camp in the early days of the fighter’s career, Leonard Ellerbe, 49, has remained the one constant, even as others fell out of favor with the mercurial champion.

But instead of serving as an assistant trainer Saturday night, Ellerbe will be wearing a suit at ringside, a full-time, fully-fledged rags-to-riches businessman. The Washington native is the CEO of Mayweather Promotions.

For the first training camp since Mayweather’s first year as a pro, Ellerbe wasn’t in the gym daily and played no role in helping the fighter physically prepare for the rematch against Maidana. Instead Ellerbe has been focused solely on the fighter’s business interests.

“It takes brains to want to surround yourself with brains,” Mayweather said in a recent interview. “I want to surround myself with the best businessmen that I can possibly surround myself with. Leonard is a very shrewd businessman.”

He’s a businessman with an unconventional background. He grew up in Northeast Washington, off Benning Road, in a two-bedroom, first-floor apartment. He slept head-to-toe in the same bed with a younger brother. His mother cleaned other people’s houses and his father cleaned other people’s cars.

Undefeated boxer Floyd "Money" Mayweather Jr. (46-0), opens up his Las Vegas gym as he prepares to fight Marcos Maidana at the MGM Grand this weekend. (McKenna Ewen/The Washington Post)

Growing up in Washington in the mid-1970s meant following the career of Sugar Ray Leonard, spending afternoons in a neighborhood gym and daydreaming about a boxing career.

“There’s not one youngster growing up in the D.C. area in that era who didn’t want to be a boxer. Fighting was a way of life,” Ellerbe said. “If you weren’t tough, people would take advantage of you.”

As an amateur, Ellerbe would travel to Las Vegas for tournaments and crossed paths with Roger Mayweather, a champion boxer at the time who’d later train his talented nephew, Floyd. Ellerbe suffered hand injuries as a teenager, and any hopes of a boxing career were dashed. He instead enlisted in the Air Force after high school and when he returned to Washington began working as a personal trainer. He built up an affluent clientele base but still leaned on his relationship with the Mayweather family.

Initially, he would fly out to Vegas on his dime to help train the young fighter, eventually rolling the dice and relocating permanently.

He “left a six-figure paying job to come work for me,” Mayweather said. “Could’ve been making $3,000 a month. . . . He worked his way to the top. He’s a multimillionaire now.”

Ellerbe didn’t have a real job description. In the gym his focus was on conditioning. Outside the gym, he was essentially on-call 24 hours a day, providing security, driving, counsel.

“If he had a verbal disagreement or got into it with anybody — if he’d done something, said something that wasn’t right — I was the one to pull him to the side and say, ‘Hey, that’s wrong. You can’t do that,’ ” Ellerbe said. “He knows if I’m talking, I have his best interests at heart.”

Over the years, Mayweather has parted ways with trainers, managers, promoters, friends, family and girlfriends. Somehow, Ellerbe not only survived, he became an integral part of the fighter’s growth, his loyalty rewarded with increasing responsibilities.

“We work hand in hand,” Mayweather said. “He understands business and I understand business. . . . I guess Leonard had the same vision I had. I guess the guys who were younger didn’t see what we seen. We had something in common. We seen a bigger picture.”

Ellerbe is credited with helping Mayweather graduate from boxer to brand, extending the fighter’s profile beyond the sport with spots on “Dancing with the Stars” and WWE broadcasts.

Ellerbe’s own business background isn’t clear. He says he earned a master’s degree in business but doesn’t say from where. “I don’t like to reveal everything about myself,” he said, noting that much of his acumen stems from on-the-job experience. He said he studied promoters such as Bob Arum, and when Mayweather was dancing on prime-time TV, Ellerbe was backstage picking the brain of Mark Cuban, another contestant.

Ellerbe and adviser Al Haymon tore up the blueprint on boxing economics, and now Mayweather essentially functions as his own promoter, which puts him in position to pocket $70 million or more off a single fight. Mayweather Promotions makes money off every ticket, beer and hot dog sold in the MGM Grand, every pay-per-view sale, every movie theater providing a closed-circuit broadcast, not to mention lucrative foreign rights. Forbes has named Mayweather the top-earning athlete in the world.

“What makes this so remarkable: This isn’t a sport that everybody watches. People get to see Floyd twice a year. But we got a model that works,” Ellerbe said.

While Haymon operates behind the scenes, Mayweather and Ellerbe serve as the face of one of sport’s most lucrative enterprise. Ellerbe negotiates, deals with other fighters, leads news conferences. He’s no longer in the gym, but he’s working hard as ever for his star fighter.

“We don’t get a chance to see each other as much, or hang out and do much any more,” Ellerbe said. “At this point, his business requires 200 percent of my focus and attention. I don’t get to enjoy the fruits of the labor all the time. Somebody has to mind the store and run the business.”