LOUISVILLE, Ky. - Black Onyx, the winner of the Spiral Stakes, was scratched from Saturday's Kentucky Derby on Friday when X-rays revealed a chip in his left front ankle, trainer Kelly Breen said. The timing of the scratch was unfortunate, because Churchill Downs sets scratch time for the Derby at 9 a.m. on Friday, and X-rays could not be taken on the suspicious ankle until after 9:30. By that time, Fear the Kitten, the lone horse on the also-eligible list, had been scratched. [2013 KENTUCKY DERBY: Get PPs, contender profiles, live updates] Breen said an initial set of X-rays was inconclusive, but a second set found what he described as a "non-displaced" chip. The scratch was then announced, shortly after 11 a.m. According to Breen, Black Onyx had a bit of swelling in the ankle on Friday morning, but he believed it was from wrenching an ankle, nothing serious, and galloped him during Friday's early-morning training hours. "I just thought he was having a bad day, slept on it wrong. But after he came back, there was a little bit of lameness, 1 on a scale of 5, a minor limp, so we ordered X-rays," Breen said. Breen said by the time he could summons a veterinarian, take jockey Joe Bravo back to his hotel, and fight through closed roads to reach Churchill Downs again, it was past scratch time. "It couldn't have been worse timing," Breen said. Black Onyx was the first Derby entrant to arrive at Churchill Downs, just days after winning the Spiral on March 23. He had appeared to train well all week. "I never saw a sign of anything," said Bravo, who was aboard Black Onyx for his final two workouts. The scratch the day before the race shows "it's tough to get" to the Derby, Breen said. Breen was awaiting consultation with veterinarians over what the next step would be with Black Onyx, but it is far from a career-threatening injury. "He'll either have routine surgery, or be given time to heal," Breen said. Black Onyx, a colt by Rock Hard Ten, has won three times in five starts. Black Onyx had drawn the rail, but Churchill Downs officials said his stall would be left open, and the remaining 19 runners would stay in their original posts.