Mourinho, winner of the Smarty Jones Stakes at Oaklawn earlier this year and fourth most recently in the Southwest Stakes, was euthanized on Monday morning at Santa Anita after suffering a severe sesamoid fracture in a front leg, trainer Bob Baffert said.
"It's terrible. He was going easily, breezing, head and head when he took a bad step," Baffert said.
Baffert is at a 2-year-old sale in Ocala, Fla. The work was supervised by his top assistant, Jimmy Barnes, who relayed the information to Baffert.
Baffert said Mourinho was working in company with another of his promising 3-year-olds, Restoring Hope.
"Jimmy said they were going along easy, just cruising around there," said Baffert, who said Mourinho was being considered for both the Rebel Stakes this Saturday at Oaklawn and the Sunland Derby on March 25.
"Up and down, every day. It's a shame," he said.
Mourinho, a son of Super Saver, raced five times, winning twice. In addition to the Smarty Jones, he won a maiden race on debut at Santa Anita last September. He also finished second in the Speakeasy Stakes at Santa Anita and the Grade 3 Bob Hope at Del Mar.
Mourinho was purchased as a 2-year-old in training last year in Ocala for $625,000. He was owned by Phoenix Thoroughbred III.