Jorge Velasquez, the only Hall of Fame jockey based at Gulfstream Park, broke his pelvis in a spill Thursday morning at Calder Race Course.

Velasquez was scheduled to replace Mike Gonzalez on Migrating Moon, the 5-1 third-choice in Saturday’s Grade I, $300,000 Donn Handicap.

After the accident, trainer Ralph Ziadie, who was looking for a seasoned stakes rider for Migrating Moon, was forced to find another replacement. Ziadie said Thursday he expected to get Jose Santos.

Velasquez, 47, was injured when a horse he was exercising for Richard Root, reportedly Valid Lupin, collapsed following the workout. Valid Lupin was reportedly bleeding through the nose at the time, indicating he was suffering severe exercise-induced bleeding in the lungs.

Valid Lupin stumbled and fell, trapping the jockey for what was described as at least a few minutes.

Velasquez briefly lost consciousness, according to agent Manuel Marrero. It was feared Valid Lupin had sustained a heart attack, but the horse eventually got to his feet on his own and did not sustain any serious injuries.

Once Velasquez was freed from the horse, Metro-Dade Fire Rescue rushed him to Golden Glades Medical Center, where he was listed in stable condition. Marrero said Velasquez is expected to remain in the hospital for about a week, and would miss at least two months of riding. No surgery is expected.

“He was trapped, but thank God the horse got up,” Marrero said. “It could have been very serious.”

Sac Stables’ Migrating Moon drew post 10 in a field of 11 at Thursday’s draw for the Donn Handicap (ESPN, 3:30-4:30 p.m.).

“Migrating Moon has been competitive in all of his races,” said Bill Mott, trainer of Take Me Out. “He is going to make everybody run.”

Lion Crest Stables’ Devil His Due, a winner of $2.6 million including the Jan. 15 Broward Handicap, was installed as the 5-2 favorite. He drew post 5 and is the 122-pound highweight.

At 3-1, starting from post 2, is Dogwood Stable’s Wallenda, an impressive winner in his 4-year-old debut here Jan. 27. Wallenda carries 118, including Herb McCauley.

Also in the race are defending Donn winner Pistols and Roses, Northern Trend, Technology, Itaka and Tropical Park Handicap winner Take Me Out. Two Fair Grounds invaders also drew into the race: Eequalsmcsquared and Far Out Wadleigh.