Horse racing’s hope for its first Triple Crown winner in 34 years were dashed Friday. I’ll Have Another, winner of the Kentucky Derby and Preakness Stakes last month, was scratched on the eve of the Belmont Stakes, ending his attempt to become just the 12th horse in history to win all three races.

I’ll Have Another experienced swelling in his left front leg after a workout Friday morning, trainer Doug O’Neill said. A doctor said it was the beginning of tendinitis.

“It’s just a freakish thing,” O’Neill told reporters outside the barns at Belmont Park. “He has been a little quiet the last few days of galloping. Yesterday we noticed some loss of definition in the leg. I prayed it was just a bit of skin irritation. This morning he looked great, but cooling down, you could tell that the swelling was back.

O’Neill said the injury was not serious enough to prevent I’ll Have Another from racing, but the decision inside the horse’s camp was unanimous to retire him before Saturday’s grueling 11 / 2-mile race, the longest of the Triple Crown races.

“It’s far from tragic,” O’Neill said, “but it is very disappointing.”

No horse has won the Triple Crown since Affirmed in 1978. In the interim, 11 thoroughbreds have won the Kentucky Derby and Preakness Stakes only to fall short in the Belmont Stakes.

Many in the horse racing community had hoped I’ll Have Another would end that drought and in the process help restore an industry whose prominence has faded amid the rise of other sports and myriad forms of legalized gambling and whose luster has been tarnished by reports of performance-enhancing drugs, lax enforcement and the breakdowns of finely bred athletes.

Racing experts debated how I’ll Have Another’s merits stacked up historically, but there was no debating the chestnut colt’s pluck. Just four months ago, I’ll Have Another was a lightly regarded colt who had been sold as a yearling for $11,000. He was later resold as a 2-year-old for a modest $35,000.

But since February, he has done nothing but prove himself a worthy champion. His riveting charge past the favored Bodemeister to win the Kentucky Derby as a 15-1 shot by 11 / 2 lengths was high drama of the razor-thin sort. And two weeks later at the Preakness Stakes, I’ll Have Another sped past Bodemeister on the final stretch again to win at the wire by a neck.

But the sport’s wait for a superhero to saddle up and ride back to prominence will continue for another year.

Speaking of I’ll Have Another earlier this week, Affirmed’s former jockey Steve Cauthen said, “I think the whole racing world is just dying to have another great horse come along and capture their hearts.”

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Photos: Past Triple Crown winners