The winner of a stakes race at Belmont Park four days ago has collapsed and died in his stall at the race track.

Sailor’s Cap won the Poker Stakes on Sunday, and trainer Jimmy Toner said in a release issued by breeder-owner Team Valor that the 4-year-old horse spiked a temperature Tuesday.

About 4:30 a.m. Wednesday, Toner said the horse “simply collapsed” and that “we are all in complete shock over this turn of events.”

Sailor’s Cap won four of 10 races, including last year’s Colonial Turf Cup.

The cause of death is unknown. A necropsy will be performed at the New Bolton Center in Kennett Square, Pa.