Internally, the agency has put its press and agent corps to work securing opportunities for select U.F.C. fighters. One such beneficiary has been the strawweight Michelle Waterson, who appeared, naked, photographed from the side, on the cover of ESPN The Magazine’s 2017 “Body Issue” in July.
Ms. Waterson, nicknamed “the Karate Hottie,” also shared her beauty secrets with People magazine and was the subject of a Power of Beauty video for Allure. At IMG’s New York Fashion Week in February, she was a celebrity guest.
While WME/IMG has the expertise in publicizing clients, it helps if they have a knack for self-promotion. The hype for the Mayweather-McGregor bout has hit a fever pitch largely because of the brash Mr. McGregor, who brings attention to himself and the sport he represents partly through his fashion choices.
At press events, Mr. McGregor, who not long ago worked as a plumber in his native Dublin, wears loud, snugly tailored custom suits made for him by David August Heil, the founder and creative director of David August in Costa Mesa, Calif.
“If two guys walk into a room and one guy is wearing a suit and the other guy is wearing a polo and chinos, you always look at the suit,” Mr. Heil said. “My motto is: We’re not just selling clothes, we’re selling power.”
Mr. McGregor, too, credits fashion for making him stand apart.
“I have transcended mixed martial arts and transcended sports in general, and my natural style and luxury tastes play a big part in that,” he wrote in an email.
At a July news conference for the McGregor-Mayweather bout, Mr. McGregor wore a pinstripe suit made for him by Mr. Heil that set social media ablaze: Those who looked closely could see that the stripes spelled a vulgar insult.
Mr. McGregor’s peacocking also helped put him on the cover of GQ Style’s spring issue.
“Fashion has become part of the Venn diagrams that need to exist in order to be a superstar,” said Will Welch, the magazine’s editor.
Grabbing eyeballs, whether through social media, television appearances or magazine covers, is especially important for U.F.C. fighters, whose bouts are often shown via pay-per-view. Those who want to watch the McGregor-Mayweather fight must pay $89.95 to Showtime PPV ($99.95 for high definition).
“Football, it’s all about stats — a lot of the athlete’s value is derived from how well he performs athletically,” said Mr. McGregor’s agent Audie Attar, who also represents National Football League players. “The guy may not need to do media, ever.”
With mixed martial arts, it’s different.
“M.M.A., it is a lot of brand building and a lot of public relations if you want to make it to top of the food chain,” Mr. Attar said. “It’s that, along with winning.”
With those demands, you can hardly blame other mixed martial artists for trying to borrow Mr. McGregor’s sartorial magic. The bantamweight champion Cody Garbrandt also wears David August suits — but he looks, at best, like a mini-Conor, and, at worst, like a mob boss on Halloween.
Mr. Heil, the suit maker, acknowledged there is some tinkering to be done with Mr. Garbrandt’s look: “Cody doesn’t have the swag to wear the same kind of suits as Conor, so we’re working on things for him now to recreate his image.”
Mr. Shapiro, of WME/IMG, said the company goes with an individually tailored approach for each fighter.
“Building the brands of U.F.C. athletes — like any other athlete or artist — is not a one-size-fits-all proposition and doesn’t happen overnight,” Mr. Shapiro said.
As in boxing, those in the lower weight classes may have a hard time getting noticed. Demetrious Johnson, known as “Mighty Mouse,” who has defended his U.F.C. flyweight title 10 times, has called out the league for not supporting smaller fighters. (Mr. White, the U.F.C. president, struck back in the press by saying Mr. Johnson’s fights do poorly on pay-per-view.)
Mr. Johnson, who is sponsored by MetroPCS, said he is frustrated that a deal with U.F.C.’s apparel sponsor, Reebok — which has signed Ms. Rousey and Mr. McGregor — has eluded him.
“I’ve asked Reebok straight to their face: ‘I’m the 10-time defending U.F.C. champion — why aren’t you sponsoring me?’” Mr. Johnson said. “They said, ‘You don’t fit the description of what we’re looking for. Ronda is a torch for women, and Conor has a country behind him.’ They want what they call ‘trailblazers.’”
This is where the association with the powerful WME/IMG can be a boon.
Stephen Thompson, a fighter who doesn’t look like one, may be an ideal crossover candidate. (He didn’t get the nickname “Wonderboy” for nothing.) With the help of the agency, he was photographed in a $3,995 Ermenegildo Zegna suit for Gotham magazine and also appeared in the influential style publication CR Fashion Book.
At 34, Mr. Thompson needs to make his name soon. “This is a very rough sport,” he said. “I see myself having maybe eight to nine years left, and I have a style where I don’t get hit as much out there.”
He has approached male models for advice on how to look at ease on camera while also carving out a defined image for himself — he’s the nice guy who teaches martial arts to 600 children in South Carolina — which has led to TV commentary spots.
“I’ve got a very small window in the U.F.C.,” Mr. Thompson said. “You have to take full advantage of every opportunity.”