Desert Deer has been put down after fracturing a leg in the Juddmonte Lockinge Stakes at Newbury on Saturday.
Kevin Darley quickly dismounted from Desert Deer in the Group One contest, which was his comeback race after a leg operation.
It was found that the six-year-old had fractured a hind fetlock and the horse ambulance was quickly on the scene to bind up the damaged leg.
Desert Deer was taken to the O’Gorman clinic in the town for x-rays.
But Joe Mercer, racing manager to owner Jaber Abdullah, said on Sunday: “He was put to sleep yesterday. He had shattered it completely from the fetlock joint down and also where he had it pinned last year. He had three screws in it.
“There was no chance of survival (could not support himself) for him so he was anesthetised a couple of hours after, as soon as we got the results of the x-rays.
“Poor old boy. He was a lovely person. I hate to see horses having to be put down.”
Explaining when the injury occurred, Mercer continued: “He travelled good. Kevin was very pleased with him and said he was moving like a clock. Two furlongs out he went to make a move on him and said he strode out and lengthened and then, bang, that was it.”
Desert Deer, who was having his first start for John Gosden at Newbury having previously been with Mark Johnston, raced 14 times for seven wins, including the Group Two Sandown Mile last season, for £156,751 (€231,000) in prize money.