Bill Farish, a spokesman for Lane's End Farm in Versailles, Ky., said the stallion became unruly while being led to his paddock Tuesday and fell on his left hind leg.
Racing for William and Suzanne Warren and trained primarily by Richard Dutrow Jr., the son of Saint Ballado earned $4,456,995 in 20 career starts over three years, the Louisville (Ky.) Courier-Journal reported Wednesday. He won nine races, came second six times and placed third once.
Saint Liam won four Grade I races last year, including the Foster and the Breeders' Cup Classic at Belmont Park, before being retired for stud and chosen as Horse of the Year.
Saint Liam stood for a $50,000 live foal stud fee and had 115 mares in foal, the newspaper said.