DEL MAR, Calif. -- Jockey Victor Espinoza was injured when the horse he was riding at Del Mar racetrack collapsed during training and died. Racetrack officials say Bobby Abu Dhabi suffered an apparent fatal heart attack during a workout Sunday morning.

Espinoza was thrown off the horse, then lay motionless for several minutes before being fitted with a neck brace and taken by ambulance to a hospital.

Agent Brian Beach says the 46-year-old Hall of Fame jockey suffered a fractured vertebra in his neck and a "stinger" to the left shoulder and arm. He says Espinoza will remain in the hospital overnight, but doctors expect a full recovery.

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"As the day went on Victor regained feeling and use of his left arm and shoulder but they are holding him overnight for observation," Beach says in a statement. "There is no timetable for his recovery or return to riding at this point."

Beach says Espinoza, who guided American Pharoah to the Triple Crown in 2015, suffered no paralysis or other broken bones. He says "it looks like we dodged a bullet." Beach mentioned that Espinoza was recovering at Scripps Hospital in La Jolla.

Four-year-old Bobby Abu Dhabi was training for the Bing Crosby Stakes next Saturday.

Brian Trump, the horse's owner, wrote on Twitter that "it is with great sadness that I can confirm this morning we lost our boy Bobby Abu Dhabi ...":