The nickname doesn't work anymore.

At the age of 36, with the scars of 48 pro fights over 12 years crisscrossing his face, Billy "The Kid" Irwin of Niagara Falls, Ont., is obviously no kid. And on this January night in Houston, in the moments before the biggest match of his life, that ill-fitting moniker seems downright preposterous. Across the ring stands Juan Diaz, the unbeaten world lightweight champ. He's just 21 years old, and looks even younger.

Tonight, Irwin is the envy of thousands of boxers who will never get the chance to fight for a world title on national TV. But shots at boxing glory always come with a catch, and this one is no different. "They think I'm the old guy -- flat-footed, face forward -- and they're just going to blow me out of there," Irwin says in the days before the fight. "They picked me to be the perfect guy to make Diaz shine." Irwin wouldn't be here if Diaz's camp thought he were a threat. There's too much riding on this young man's success.

In the modern world of pro boxing, where being entertaining is as important as being good, Diaz has everything it takes to be a star. He is the son of working-class Mexican immigrant parents, articulate in Spanish and English, and studying toward a degree at the University of Houston. In the ring he is a ball of fire: a rare mix of speed, smarts and power, who throws punches in wild bursts.

If Diaz is the made-for-TV champion, Irwin is his made-for-TV challenger. With a career record of 43 wins and five losses, he has a decent enough track record. Perhaps more importantly, he's never been knocked out. Irwin is as tough as they come. He can be counted on to show up, fight hard, and ultimately he can be expected to lose -- another stepping stone in the ascent of a new boxing superstar.

But Irwin has other ideas. By taking this fight, training hard for it, and allowing himself to believe he can actually win it, he is engaged in an act of defiance against the power structure of pro boxing: the byzantine network of promoters, commissions, agents and officials who choreograph the sport. For years, he's been on the margins of the big time. Now, in the dusk of his career, he's cast as a supporting character in Juan Diaz's story. This is Irwin's one chance to steal the show, and make his own Hollywood ending.

Five nights before the fight, and there's a problem. We're in the Shamrock Boxing Club, in Niagara Falls -- a single room, about 60 feet long and 20 feet wide, with four heavy punching bags hanging from chains drilled into the ceiling and a ring at the far end. I ask how he's feeling and he shakes his head in disgust. "I'm sick," he says. "Everything was going perfect, and now I got a cold." His long-time friend and trainer, Dave Morris, tries to stay positive. Billy's better today than yesterday, he says, and there's still time to recover. But Irwin is clearly worried.

As we lean against the wall and watch a kid no older than 12 learn to throw a proper jab, Irwin calmly explains he's had enough. This will be his last fight, win or lose. He still loves the sport, and insists he doesn't feel too old. But he's got a wife and two young children now, and a job in security at a local casino. Except for two detached retinas in 1996, he has somehow avoided serious injuries. He doesn't want to be another one of those guys who can't let go. His mind and speech are still sharp, and he plans to keep it that way. "This is it," he says. "If I lose, I lose to a 21-year-old champion. But if I win, I go out on top." This is the hopeful fantasy of the aging fighter: the dream of turning around a career of disappointment with a single moment of ineffable glory.

As an amateur, Irwin was four-time national champion. He represented Canada at the 1991 PanAm Games in Cuba, and the 1992 Barcelona Olympics. But as a pro he never made it into boxing's exclusive club of contenders. His one previous shot at a world title came in 2000, when he lost a dull 12-round decision to Paul Spadafora. In his next fight, he lost to a virtual unknown named Dorin Spivey. The experts said The Kid was finished, and for the next three years Irwin fought to prove them wrong. He won nine straight fights, all to rebuild his reputation.

Pat Kelly watched all this with a mixture of pride and regret. He owns the Shamrock and has known Irwin since 1984, when Billy was a smooth-faced 15-year-old who wanted to learn to box. "He's got knockout power with both hands," Kelly says. "And he's smart. He talks like a Shakespearean actor." But he never could break into the elite. "Billy had a lot of bad managers over the years," he says. "You can't just be a good boxer from a small club and work your way up. That's not how this business works."

On the nightbefore the fight, Irwin is in bed, and I'm in the hotel bar with his small entourage, talking about how he's going to shock the world. Diaz has never been hit, we say. He has only 12 knockouts in 26 fights, so he obviously doesn't have enough power to break a pane of glass. And there are rumours he's already negotiating his next title defence. He's taking Irwin lightly. These are the lies we tell each other, over and over, so often we almost believe them. But on fight night, reality comes quickly into focus.

A crowd of about 3,000 jams into the Reliant Center, most of them from Houston's working-class Hispanic neighbourhoods, where Diaz is fast emerging as a hero. They wave Mexican flags, chant Diaz's name and hoot at the bikini-clad card girls. Their adulation is momentarily diverted when Roger Clemens is introduced. The great baseball pitcher has just re-signed with the Houston Astros for US$18-million a year, and now he's at ringside watching the action. The cheers are replaced with loud boos when Irwin walks in, and then with euphoric screams and chants of "MEH-HE-CO" when Diaz appears.

When the bell rings, Diaz marches forward and goes to work, snapping jabs off Irwin's forehead, and backing him up. About a minute into the fight, Irwin's back is pinned to the ropes and Diaz is picking him apart with devastating combinations: jab, hook, hook, hook. Left to the head, right to the body, left to the body, right to the head. When the bell rings to end the first round, the reporters on press row are already writing their stories about how the local phenom pummelled the veteran from Canada.

In the second, it seems like the end is near. Irwin tries to throw a left at Diaz. The champ beats him to the punch with a wicked right hook to the head that sends Irwin stumbling into the turnbuckle. Diaz storms after him, unleashing a flurry of punches. Irwin hunches over trying to cover up, and finally slumps down to one knee. It is only the second time he has ever been floored. He doesn't look angry, just disappointed.

Irwin is staggered again in the third, but won't fall. Diaz backs him to the ropes again, and fires away. Irwin tries to punch his way out of trouble, as he has done for his whole career. But that Billy Irwin power is gone. Even when his fists find their mark, they do nothing to slow Diaz's assault.

The crowd keeps waiting for Irwin to drop, but he will not. The fourth, fifth, sixth, seventh and eighth pass, with Diaz raining hellfire on Irwin as he leans back against the ropes, pulling his gloves up to his face in a vain attempt to block. Morris yells orders that the fighter can't act on. He urges, then commands, and finally begs Irwin to move off the ropes. But he doesn't move. With every punch it becomes clearer that Diaz has found the stepping stone he was looking for, and Irwin's dream ending slips further away.

After the eighth round, the ring doctor is closely examining Irwin's badly swollen and bloody right eye, but he doesn't stop the fight. Diaz sits in his corner with his legs stretched out in front of him, like he's relaxing in a sauna, calmly nodding at his trainer.

One minute and 27 seconds into the ninth round, Irwin backs again into the ropes. Diaz snaps Irwin's head back with a left, and then another right hook to Irwin's mangled eye. With that, the referee steps between them and waves his arms in the air, bringing an end to the onslaught, and to Billy Irwin's career. It is a technical knockout, the first he has ever suffered.

As Irwin climbs down from the ring, the cameras swarm around Diaz. Clemens walks over and shakes Irwin's hand. "You fought a good fight," he says, and taps a finger on his chest. "What you've got in there, you can't teach." Irwin just thanks him and moves along. He is downcast but stoic. He blames his lack of power on lingering effects of his cold, and insists he wasn't hurt by any of the 238 punches he took in just over 25 minutes of mayhem -- but surely that's just pride talking. A reporter asks what he'll do now. "I'll go raise my family, and go back to work," he replies, with no hint of regret.

An hour after the fight, we're in the cavernous backstage change area, when Irwin turns to me. With his eye socket reduced to a puffy purple slit, he says, "Sorry." I'm stunned, and finally tell him I don't think he has anything to be sorry for. He shakes his head again and says, "It wasn't meant to be." Then he looks at my notepad and says, "Just try to be positive, okay?"

It's hard to be upbeat about watching a man take the beating of his life at the very moment he most wanted to shine. It's hard not to focus on the merciless cruelty of the sport. But that's life, that's boxing, and Irwin knows that better than most. His only fear was of disappointing those who believe in him, of being remembered as a loser. But no one who witnessed his Houston finale could be left with that image. Irwin walks away with class, with his faculties intact, accepting the way it all turned out, without bitterness or complaint. And as one of the toughest fighters Canada has ever produced.