Julio Diaz is a two-time IBF lightweight champion. On Saturday, he'll fight Juan Diaz at the Sears Centre in Chicago with his title on the line, as well as his opponent's WBA and WBO belts.
He's one of the game's most entertaining performers.
But he'll never forget the fall of 2003.
"No matter what I do, how far I go, I'm always going to remember that," he says through gritted teeth.
Top Rank was making a match for the late fall for Floyd Mayweather Jr., a bout that would be televised on HBO. It proposed Diaz as the opponent, with the bout to be held in Mayweather's native Grand Rapids, Mich.
Diaz, 27, didn't have a concern about the location. He grew up in a family of boxers and never once was fearful in the ring.
Plus, he'd sparred frequently with Mayweather. He desperately wanted the fight, to not only emerge from the shadow of his older brother, Antonio, but also to decisively make his stamp on the game.
"I know the gym is the gym and you can't compare it to fights, but I had worked with Mayweather for three weeks (earlier) and I had no trouble with him," he said. "There is a style for everyone. Mayweather is a great, great champion, don't get me wrong, but there is someone for everyone.
"No matter how good you are, there is someone out there who has the style to beat you. And I really felt that I could win that fight."
The problem was, he never got the chance. HBO officials, concerned about a first-round knockout loss he suffered at the hands of unheralded Juan Valenzuela, declined to accept him as an opponent.
They chose Phillip N'dou instead.
"He was a guy who was once considered a top prospect in the world and Shane Mosley had told me how good he was, which I had always remembered," HBO's Kery Davis said of Diaz. "But then there was that loss (to Valenzuela) and that left a bad taste in terms of him being ready for someone like Floyd Mayweather.
"He hadn't had the type of victory since (losing to Valenzuela) that really made you confident he was ready for Mayweather. He was a very good prospect and he's proven since that he is a world-class guy. But it's tough to pick guys to fight someone like Mayweather and there was that question mark at the time about Julio."
While it cost him a big payday, valuable exposure and perhaps a chance at a stunning upset, it's turned out to have been a good thing for Diaz (34-3, 25 KOs).
"It was humiliating," he said. "I have always worked hard and tried to be as professional as I could, but I made a commitment that I would work even harder after (being bypassed) that to prove that was a mistake that should never have happened."
He'll get a chance to make a big statement on Saturday when he takes on Juan Diaz, an affable wannabe attorney who has suddenly risen to the top of the heap in the 135-pound division.
Juan Diaz, 24, has always been a fearless and a busy fighter, but he's never been regarded as a puncher.
But after he systematically took apart Acelino Freitas in April, that perception is beginning to change.
"I guarantee you, I won't underestimate his power or anything else about him," Julio Diaz said. "He's good. He's very good."
Juan Diaz (32-0, 16 KOs) turned professional at the same time as many who competed in the 2000 Olympics. He had earned a spot on the 2000 Mexican Olympic team, but was later told he was three months too young to compete.
So when he turned pro, he had little fanfare. All of that went to Jermain Taylor, Jeff Lacy, Ricardo Williams, Rocky Juarez and Francisco Bojado.
But when the bell rings on Saturday, none of them are more accomplished than Juan Diaz.
"He was a guy who at the time didn't really get a lot of attention or notice," Davis said of Juan Diaz. "But look what he's done: He's still undefeated, he never takes a step backward, he has one of the most fan-friendly, telegenic styles you could hope to find and he's the kind of guy you instantly like when you get to know him."
Both men, who are not related, share that trait. They're easygoing to a fault and aware of their privileged station in life.
But they each plan on inflicting plenty of harm for however long the fight lasts on Saturday.
"I think people still doubt me a little," Juan Diaz said. "Nobody has been able to back this guy up. If I can go out there and do that and back him up and hurt him and win this fight impressively, that is really going to enhance my reputation."
Juan Diaz has spent hours watching tapes of Julio, though Julio professes not to have watched a shred of tape of Juan.
But it's clear he knows what he's up against.
"If I wasn't fighting in this division, I would be a fan of his," Julio Diaz said. "He's a tough, strong fighter. But I have fought those kinds of guys all my life. I haven't been protected. I took the tough guys on short notice. I fought all the big prospects.
"Ever since I turned pro, it was one after the other. Taking on tough guys is nothing new to me. And neither is winning. That's what I do. I'm a winner."