The horse was Chelokee, trained by Michael Matz, who was quickly on his way to Rood & Riddle Equine Hospital, about an hour away in Lexington, Ky.

"He appears, on first exam, to have a condylar fracture that then affected the stability in his ankle," veterinarian Larry Bramlage said. "That's amazingly very similar to what Barbaro had, only in another leg."

"He was traveling absolutely perfect," said jockey Ramon Dominguez, who was tossed by the horse at the top of the stretch. "I had the best horse in the race. I was just trying to pick my spot, and as soon as he got to the top of the lane, he switched to his right lead and broke down."

Dominguez said there was "absolutely no contact" with another horse.

Last night at 7, Bramlage, reporting as part of the American Association of Equine Practioners' "on-call" veterinarian program, said that Chelokee had arrived at Rood & Riddle "in good order and that the first priority would be reestablishing blood supply to the colt's injured right front leg."

Barbaro, the Kentucky Derby winner trained by Matz, shattered his leg in the 2006 Preakness Stakes and was euthanized eight months later at the University of Pennsylvania's New Bolton Center after complications from laminitis.

Yesterday, the horses were running on a sloppy track, but other trainers and jockeys said it wasn't a treacherous surface. Chelokee probably would have been the favorite in the $150,000 Alysheba Stakes, but the horse had never run on a sloppy track. Matz had said earlier in the week how pleased he was with how the 4-year-old had been training after a nine-month layoff on a farm. In his return, Chelokee won a $75,000 race at Gulfstream Park on March 29. He won the Barbaro Stakes last year at Pimlico.