LOUISVILLE, Ky. - The Breeders’ Cup turned tragic in the $2 million Distaff on Saturday when the filly Pine Island was euthanized after breaking down on the backstretch.

Round Pond won the Distaff, but the victory was marred by Pine Island’s fatal injury. Fleet Indian, the 8-5 favorite, also was injured later in the race but her injury appeared treatable.

Pine Island was euthanized after dislocating her left front ankle, which broke the skin and introduced infection into her bloodstream, according to Dr. C. Wayne McIlwraith, an on-call veterinarian Saturday at Churchill Downs.

Jockey Javier Castellano was pitched over the top of Pine Island as the 3-year-old filly tumbled to the ground. He gave a thumbs-up sign as he got into an ambulance, and was expected to be aboard Bernardini later in the Classic.

Fleet Indian sustained ligament injuries in her left front fetlock joint, which is repairable, said McIlwraith.

There were few smiles in the winner’s circle from Round Pond trainer Michael Matz and jockey Edgar Prado, who endured similar heartbreak when Barbaro took a devastating misstep in the Preakness Stakes in May.

Barbaro’s injury ended his career, and he is still recovering.

“I’ve been in that situation and nobody ever likes to see that happen,” Matz said.

The 1990 Distaff was the scene of another horrifying breakdown.

Go For Wand snapped her right front ankle just past the sixteenth pole at Belmont Park. She got up and hobbled on three legs, with the mangled part of her fourth limb dangling grotesquely before she collapsed. She was euthanized in front of the grandstand.

Earlier, Street Sense pulled a big upset, and now has a big burden to carry into next year’s Kentucky Derby.

After a record-setting 10-length win in the $2 million Juvenile, Street Sense now becomes the early Derby favorite saddled with trying to break a 23-year-old jinx: No Juvenile winner has gone on to win the run for the roses.

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“I don’t believe in anything,” Street Sense’s trainer Carl Nafzger said. “The only problem we got in winning the Derby is we’re 1 in 18,000. There’s 18,000 other colts out there to run at us. You’ve got to be ready on this Saturday and that Saturday.”

The Juvenile was the second of eight races at the $20 million Breeders’ Cup. The $5 million Classic, matching East Coast star Bernardini against West Coast star Lava Man, was set for later Saturday.

Street Sense, ridden by Calvin Borel, was certainly ready to win on this crisp autumn day at Churchill Downs. The 2-year-old shot through along the rail to win by the largest margin in the Juvenile’s 23-year history — and second largest in any Breeders’ Cup race.

“I didn’t expect that kind of performance, but I knew that he was a freaky kind of horse,” said Nafzger, best known for saddling 1990 Derby and Breeders’ Cup Classic winner Unbridled. “We love to win at Churchill. He’s my Derby horse. I’d be a fool to say he wasn’t.”

Trainer Todd Pletcher, with a record 17 horses in the Breeders’ Cup, was 0-for-15 through the first seven races. But he was happy with 3-1 favorite Circular Quay’s second-place finish in the Juvenile. The colt was pinched at the start and far back in the field of 14 through the first five-eighths of a mile.

“I thought Circular Quay ran a huge race,” Pletcher said. “He dropped way back and circled the field. He was just second best.”

Pletcher’s two other colts, Scat Daddy and King of the Roxy, ran fourth and eighth, respectively.

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Borel saved ground along the rail most of the way, then Street Sense found an opening at the top of the stretch and burst through for his second win in five starts. He covered 1 1-16 miles in 1:42.59.

Sent off at 15-1 odds, Street Sense paid $32.40.

In earlier races before the Classic: Juvenile Fillies:

Dreaming of Anna left her owner with tears in his eyes after an emotional victory in the $2 million race.

Named after owner Frank Calabrese’s sister, who died of cancer 16 years ago, Dreaming of Anna took the lead early and beat Octave by 1½ lengths to remain undefeated in four starts.

Calabrese’s eyes welled with tears on his 78th birthday, and he was too choked up to talk immediately after the race. Later, he said he would consider running his filly in the Kentucky Derby.

“If she stays healthy, I think she can do it,” he said.

Dreaming of Anna likely clinched the 2-year-old filly championship in beating 13 rivals.

Ridden by Rene Douglas, Dreaming of Anna covered the 1 1-16 miles in 1:43.81 and returned $7.20 to win. The slight 5-2 favorite is trained by Wayne Catalano.