HALLANDALE BEACH, Fla. -- Monarchos' biggest victory was also his last.

The gray colt who rallied from 13th place to win last year's Kentucky Derby has been retired to stud because of an ankle injury, trainer John Ward said Monday.

Monarchos' latest injury apparently occurred while galloping last week in preparation for the $500,000 Donn Handicap at Gulfstream Park on Feb. 9. An ultrasound revealed a damaged ligament below the left front ankle.

"He dinged himself, but it didn't appear to be at all serious," Ward said. "He didn't seem quite right after that, though, and we had an ultrasound done on him."

Monarchos, the son of Maria's Mon, retires with earnings of $1.72 million. He was purchased by John Oxley in Miami in 2000 for $170,000. Stallion plans will be announced later.

This has been a difficult time for Ward, whose assistant trainer, Yvonne Azeff, was seriously injured in a training accident Saturday at Gulfstream. The 41-year-old Azeff remained in a coma Monday, but doctors expect her to make a full recovery.

Monarchos won all three of his starts at Gulfstream as a 3-year-old, including the Florida Derby. He took second in the Wood Memorial at Aqueduct, then won the Kentucky Derby by 4¾ lengths with the second-fastest time in race history, behind only Secretariat.

But that dramatic comeback was Monarchos' final victory. He finished sixth in the Preakness and third in the Belmont, then was sidelined by a hairline fracture in his right knee.

He raced just once after that, finishing third as the heavy favorite in an allowance race Jan. 19 at Gulfstream. Following that start, Ward and jockey Jorge Chavez said they were still optimistic about his chances in the Donn.

Monarchos' retirement further weakens the Donn field. Trainer Bobby Frankel earlier decided not to ship standout California colt Lido Palace to Florida for the race.