Birdstone, who denied Smarty Jones the Triple Crown by beating him in the Belmont Stakes, has been retired from racing due to an ankle injury his connections announced Wednesday.

No stud plans were set.

During routine radiographs taken following Birdstone's seventh-place finish in Saturday's Breeders' Cup Classic at Lone Star Park, Birdstone was found by Dr. Joe Migliacci to have a chip in his left front ankle. The chip is located at the top of the pastern bone where the ankle joint meets the cannon bone, Migliacci said.

While the chip could have been addressed via surgery, owner and breeder Marylou Whitney, her husband, John Hendrickson, and trainer Nick Zito decided to retire the colt instead.

"The Whitney's didn't want him to go through surgery,'' Migliacci said. "Even if it's a very, very small chip, [Birdstone] could come out of it very well, but it's unpredictable whether he could compete at the Grade 1 level.''

Whitney, through Hendrickson, said, "We decided Birdstone owes us nothing. We owe him everything.''

Hendrickson added that it was disappointing because he and Whitney were looking forward to running Birdstone as a 4-year-old, particularly in the Whitney Handicap at Saratoga and the Breeders' Cup Classic at Belmont Park, where Birdstone is 2 for 2.

"This breaks our hearts,'' Hendrickson said. "But it's always been about the horse, not about us.''

Birdstone, the first horse since Easy Goer to win the Champagne, Belmont and Travers, was shipped from Texas to Louisville, Ky., on Wednesday. Birdstone will be stabled at Churchill Downs until stud plans are finalized.

Birdstone, a son of Grindstone out of the mare Dear Birdie, packed a lot into a nine-race career. He won his career debut by 12 1/2 lengths at Saratoga before finishing fourth in the Grade 1 Hopeful. He won the Grade 1 Champagne at Belmont in his final start at 2.

At 3, Birdstone finished fifth as the 3-5 favorite in the Lane's End Stakes at Turfway Park and eighth in the Kentucky Derby. After skipping the Preakness, Birdstone ran down Derby and Preakness winner Smarty Jones in the final sixteenth to win the Belmont at odds of 36-1. Whitney felt compelled to apologize for the victory, as a record crowd and national television audience were hoping Smarty Jones could win the Triple Crown.

Despite a 12-week layoff, Birdstone won the Travers impressively. Birdstone was sent off the 6-1 third choice in the Breeders' Cup Classic, but never threatened.

Birdstone, a half-brother to 2003 champion 3-year-old filly Bird Town, retires with a record of 5-0-0 from 9 starts and earnings of $1,575,600.