LAS VEGAS — Losing has not been in Floyd Mayweather’s vocabulary for more than 20 years, not since he was on the receiving end of a dubious decision in the semifinal bout of the Atlanta Olympics.

Conor McGregor, despite occupying the wildly unpredictable world of mixed martial arts, has had just a single slip-up since joining the Ultimate Fighting Championship.

Yet when they square off at T-Mobile Arena on Saturday and box their way to a mind-blowing payday, it will be the pinnacle of an adventure that may not have happened without the one thing that neither of them likes to contemplate: defeat.

“I have lost,” McGregor said recently. “I can say it and I can own it. And I have come back and I have learned from it and I have taken it for what it is. It is an experience to grow from. It is a test of your mind and how strong you are.”

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McGregor was already the UFC’s biggest name in March 2016, thanks to his explosive 13-second knockout of Jose Aldo three months earlier. However, in losing to Nate Diaz in a submission upset, then avenging that loss before claiming a second UFC title at lightweight, he truly captured the public imagination.

A staple of script writing dictates that the action hero must solve his own problems, and by immediately agreeing to a rematch with Diaz, at the same, higher, 170-pound limit, McGregor cemented his reputation as a fighter unfazed by any obstacle.

“If you get me, you get me, and I will stand up and shake your hand and say ‘fair play’ and I will get you next time,” McGregor said. “I am not the kind of man who is deterred by setbacks in life. You show me someone who has never had a disappointment and I will show you someone who was not brave enough to challenge themselves and try for difficult things.

“If I hadn’t lost to Nate then maybe I wouldn’t be as strong in my head. Little things in my overall game would not have been fixed. My stamina and my approach to all that would have been different.

“That is the character of a man. You look at yourself in the mirror and work out how to get better and then you go out there and you put in an insane amount of work and you do it.”

Mayweather has not lost since turning pro in 1996 and has not come particularly close, with the exception of his controversial win over Jose Luis Castillo in 2002, a bout most observers thought Castillo won.

He does have a blemish on his otherwise impeccable record though, that Olympic defeat to Bulgaria’s Serafim Todorov in Atlanta. Mayweather was an overwhelming favorite and appeared to control the fight, but the judges gave it to Todorov by a 10-9 margin.

“We all know I got ripped off,” Mayweather said at the time. “It’s time for me to turn professional. I can’t deal with amateur boxing anymore.”

Years later, before facing Robert Guerrero in 2013, he reflected that the setback had been a powerful motivator.

“I am happy with how it turned out,” Mayweather said. “Gold medals don’t put money in your bank. It didn’t feel good at the time but it is not something I think about a lot now.

“When something like that happens, you don’t want it to happen again. I felt like something had been taken away. I knew I didn’t want to have that feeling again, and I haven’t. That’s why I control my career, and I control my destiny.”

Mayweather did not expand upon the ways in which the Todorov loss had boosted his subsequent exploits, but his advisor Leonard Ellerbe said that the fear of defeat still pushes him and will ensure he is fully focused before his scrap with McGregor.

“(Defeat) has never happened to him as a professional,” Ellerbe said. “There have been times when he has been hurt and buzzed. But I think it made him realize that it is not fun to lose, no matter what the circumstances.

“That is why we don’t overlook anybody. Going 49-0 does not happen by chance. It does not happen because you got lucky a few times. It happens because you prepare every single day for every single fight, and you prepare like it is going to be your last.

“A lot of fighters, they get comfortable. It is hard, man. Over time it is hard to keep going back to the gym when no one is watching, and just putting in that effort every day.”

Follow Martin Rogers on Twitter @mrogersUSAT.