Floyd Mayweather Jr does not lose much and he does not take losing well. Unbeaten in 38 bouts as a professional, Mayweather also had a stellar amateur career, winning 84 of his 90 bouts. Two blocks off the Strip, stands Barry’s Boxing, a smart roomy gym in a road populated by warehouses and strip clubs. Inside, Augie Sanchez is training boxers whom he hopes will be the champions of tomorrow, but few realise that Sanchez is one of the six who beat the “Pretty Boy”.

“I would say he was upset, yeah, very upset. I’d never seen him that upset before,” Sanchez said of his victory in the 1996 United States Championships. The bout had finished 11-11, but Sanchez won on countback. It was the only one of four bouts against Mayweather that Sanchez had won.

He lost to him twice in the US Olympic trials, which secured Mayweather the featherweight position at the Atlanta Games, where he won bronze. “We were teammates in 1994. He was 112lb and I was 125lb, so they bunked us to a room together,” Sanchez, 30, said. “He really wasn’t arrogant, he was pretty low-key. The next year, he jumped two weight classes to my division and we ended up fighting. When you’re in that ring, you leave your friendship outside. We fought four times and I honestly believe he only beat me one time.

“Floyd hasn’t really changed much since the amateurs, but he has a little more snap, he has good condition and he works hard. He’s trained in this gym and we talk and he’s a good guy.”

Sanchez is best remembered in Britain for his WBO featherweight title challenge against Naseem Hamed in 2000. That night, he put Hamed on the floor before being knocked out in the fourth round. Now Sanchez says he is content as a trainer. “Maybe one of these guys here will be as good or better than I was,” he said.

So how do you beat Mayweather? “It was all heart and perseverance,” Sanchez said. “If Ricky tries to outbox Mayweather, it isn't going to happen, but I think it is going to be a good fight because he’s a pressure fighter, just as I was.”

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