It was the same injury that ended Seabiscuit's reign as a champion race horse. But as I'll Have Another came down with a sudden flare-up of tendinitis on the eve of racing for the elusive Triple Crown, there is a sense that the sport needed this victory more than the horse and his owners.

With a record 120,000 people preparing to descend upon the Belmont Stakes on Saturday, the horse's trainer broke the bad news: I'll Have Another had suddenly come up lame. It was a grim turn of events for what was expected to be one of the sport's best shots at a Triple Crown since 1978, when Affirmed won the Kentucky Derby, Preakness and Belmont in dramatic fashion.

As conspiracy theories of a potential failed drug test spread, the horse's trainer, Doug O'Neill, told a press conference that tendinitis was to blame. It was an explanation met with skepticism, since Mr. O'Neill carries a record of suspensions in the sport, but race organizers confirmed the horse tested clean. Instead, it was a common injury that befalls many horses – probably a twisted leg, no one really knows – that forced the three-year-old colt to the sidelines and ultimately into retirement. I'll Have Another will now command millions as a stud horse, breeding a new generation of race horses. "It's far from tragic, but it's really disappointing," Mr. O'Neill said.

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Like Seabiscuit, the horse that captivated North America in the 1930s, I'll Have Another is an underdog story. Bought for a relative pittance, he showed a gift for winning, including the first two legs of the Triple Crown.

"The fact is, horses are fragile. You look at a half-ton body on those spindly, little legs, They get hurt a lot," said Andy Beyer of the Washington Post, one of the longest serving horse-racing columnists. "What happened to I'll Have Another would not have been an extraordinary thing unless it was a horse trying to win the Triple Crown for the first time in 34 years."

Canadian trainer Sid Attard had a similar thing happen with Numerous Times as the horse made a run for the 2001 Breeder's Cup. The first thing trainers noticed was heat from the tendon, then swelling. "We knew right away," Mr. Attard said. "It's just one of those things. Horses run today, they're fine, then they do something overnight, like kicking in the stall."

But with horse racing losing audiences, a Triple Crown was seen as perhaps the one feat that might rejuvenate the sport amid dwindling revenues, allegations of doping and questions over animal safety. "I'm not a rooter in these races, but I really wanted to see this horse win," Mr. Beyer said. "Racing just needed one good, positive story."

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The Belmont curse

I'll Have Another was supposed to be a runaway tale; the Canadian-owned thoroughbred set to become the 12th horse to win one of sports most celebrated titles, racing's Triple Crown.

Who knew that I'll Have Another actually meant we were doomed to another round of disappointment and more talk of curses?

Heavy now is the jinx that rests upon the sport of kings. With I'll Have Another scratched by a sore tendon, the list of horses that have won the Kentucky Derby, Preakness and Belmont Stakes in successive order remains stuck at 11 over a staggering 137-year period.

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It's as if turning the triple in horse racing has joined the Toronto Maple Leafs' pursuit of a Stanley Cup as an impossibly ill-fated venture.

The last horse to win it all, Affirmed in 1978, capped a six-year span that saw three horses earn lasting fame (Secretariat in 1973, Seattle Slew in 1977). But since then, it's been all tease and no finish with some odd twists tossed in for sour measure. Here's what we're talking about:

Spectacular Bid was the four-legged star of 1979 and everything was going along smoothly until someone dropped a safety pin. The three-year-old stallion happened to step on it, got the pin embedded in its hoof and developed an infection. Given medical clearance, Spectacular Bid ran in the Belmont and had an early lead before losing ground and coming in third. Thus began the curse of the Triple Crown's modern era.

And it has only gotten worse.

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In 1987, Alysheba had to do the Belmont without his medication (Lasix, an anti-bleeding drug that can improve overall performance) because it was banned in New York racing circles. Alysheba ended up fourth; the winner, Bet Twice, was first by a comfortable 14 lengths. Two years later, Sunday Silence was expected to win but lost to Easy Goer, a rival Sunday Silence had already beaten in the Kentucky Derby and Preakness.

Real Quiet galloped hard to the wire at the 1998 Belmont only to lose by a nose to a horse (Victory Gallop) that had been stricken by ringworm. Charismatic turned out to be just as star-crossed in 1999. He suffered fractures in his front left leg during the Belmont and lost to Lemon Drop Kid.

Yet even those stories don't hold a whip to what vexed War Emblem and Big Brown.

War Emblem stumbled out of the Belmont gates in 2002 and nearly dropped to his knees. After a spirited recovery, he ran out of steam and finished an embarrassing eighth. As for Big Brown, he won the first two legs of the 2008 Triple Crown then injured a hoof and pulled up in the Belmont and did not finish.

There are natural, concrete reasons why it's so difficult for a horse to win three high-profile races in a row. Current scheduling requires that all three events are staged over five weeks. The Kentucky Derby is held the first Saturday in May, the Preakness goes two weeks later then the Belmont Stakes three weeks after that.

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Known as the Test of the Champion, the Belmont is the longest, most demanding race (1½ miles in length) and puts a premium on endurance. The majority of today's race horses are bred for speed, and while that can carry them to the Belmont, it can't always help them win, as Smarty Jones discovered in 2004. On a June afternoon at Belmont Park, Smarty Jones had the lead until surrendering it in the stretch for the first time in his career.

The winner ended up being Birdstone, a 36-to-1 long shot.

For 34 years now, that's how the Triple Crown gets played every time.

The twinge heard round the world

I'll Have Another injured the superficial tendon on his left foreleg, which runs down the back of the leg from the knee (or hock). Tendons attach muscles to bones, and are cable-like structures made of long bundles of fibres. Injuries occur when these fibres stretch or tear during exercise. Initial signs of injury include heat and swelling, and an ultrasound confirmed the damage to I'll Have Another's superficial tendon, the most common type of tendon injury in athletic horses. It will take at least six months of rest and controlled exercise to heal, trainer Doug O'Neill said, but it can be difficult for thoroughbred racehorses to return to peak form. "He's done enough," owner J. Paul Reddam said.

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The Canadian fans

At Mario Gutierrez's home track in East Vancouver, the show, as they say, will go on: A party planned at Hastings Park today will proceed, as friends and supporters try to buoy heavy hearts.

"I'm just ill. Just terribly disappointed," said Drew Forster, the jockey's former agent in Vancouver. "Disappointed hardly even explains it."

Organizers of the party, which will feature a 40-foot screen and DJs, expect a large turnout. "We know Mario's going to probably look at the feed from Belmont, of what's going on at Hastings, and we're hoping to have a record crowd out," said Howard Blank, vice-president of the Great Canadian Gaming Corporation.

The ratings

A television audience rivalling the Super Bowl was projected to tune into NBC Saturday for the Belmont Stakes. But as I'll Have Another came down with tendonitis, the TV network felt the pain. Plans to expand the day's coverage beyond the six hours originally allotted were shelved. "While we are obviously disappointed," NBC spokesman Adam Freifeld said, "the Belmont Stakes is still an iconic event on the sports schedule, and [NBC] will treat it as such."

The odds

A $100 wager on I'll Have Another would have yielded just $180 if the horse won the Belmont Stake. But with the overwhelming favourite now scratched, bookmakers are scrambling. Pundits began parsing the field for a new favourite, which may include Dullahan, Union Rags or Paynter. "There are really only three horses that can win the race, the rest of them are really weak. I'm afraid this is going to be a crashing anti-climax," said racing columnist Andy Beyer of the Washington Post.

With files from Hayley Mick and Andrea Woo