Galileo Gold, Hugo Palmer's 2016 QIPCO 2000 Guineas winner, has been retired after suffering an injury earlier this month.
The four-year-old appears to have picked up the injury in his run in the Al Shaqab Lockinge Stakes at Newbury on May 20.
The colt had excelled through the early part of the 2016 season, claiming Classic glory at Newmarket before finishing second in the Irish equivalent at the Curragh as well as winning the St James's Palace Stakes at Royal Ascot.
The son of Paco Boy was also second in the Sussex Stakes at Glorious Goodwood, but could not add to his tally in the Prix Jacques le Marois or Queen Elizabeth II Stakes, and had to settle for fifth at Newbury on his reappearance.
It is understood the soft tissue injury was then discovered, and the decision has now been made to retire the horse and send him to stud.
Galileo Gold ran in the colours of Al Shaqab, whose racing manager Harry Herbert said: "It's a great shame, real sadness all round. It's a soft-tissue injury that meant we couldn't carry on with his career at this stage of the season. It's very sad.
"His run in the Lockinge was very disappointing, but obviously in the cold light of day there's a reason for it. It's a shame we couldn't go on with his career because the horse has absolutely exploded from three to four.
"Everyone who saw him in the Lockinge would agree with that. He had been working very well.
"He has been a terrific flag-bearer for Al Shaqab and provided us with our first Classic winner and of course it was a wonderful season with the St James's Palace Stakes victory as well, plus a second in Ireland (Irish 2,000 Guineas) and a great run in the Sussex Stakes.
"All credit to Hugo Palmer and his team, who have done such a fantastic job with him."
Herbert added: "He'll go to stud, but no decision has been taken on that. It's still very much in the melting pot.
"We were very excited what he might achieve this year, but he's a great looking horse, with a great pedigree, good constitution and a fantastic brain. He has a lot of ticks in the right boxes for a stallion career ahead."
Palmer's charge won five of his 12 career starts - including the 2000 Guineas - earning £960,886 in prize-money.