St Nicholas Abbey's racing career is over after picking up a serious injury at Ballydoyle on Tuesday morning.
The six-times Group One winner was being prepared for a crack at the King George VI And Queen Elizabeth Stakes at Ascot this weekend.
A statement posted on the Coolmore twitter feed read: "St Nicholas Abbey suffered a serious career ending injury at Ballydoyle this morning, vets are currently attending to him.
"We hope to save him for a career at stud, a further update will be posted later."
A son of recently deceased champion sire Montjeu, St Nicholas Abbey was champion two-year-old in 2009 when he crowned his season with a blistering display in the Racing Post Trophy at Doncaster.
He was a red-hot favourite for the 2000 Guineas the following year, but could only finish sixth behind Makfi, and was not seen again until the following April when beaten at the Curragh.
He returned to something like his juvenile form when an easy winner of the Ormonde Stakes at Chester and went on to further Group One glory in the Coronation Cup at Epsom, a race he would win on a further two occasions.
Arguably his two greatest successes came on the world stage, however.
He won the Breeders' Cup Turf in 2011 from Sea Moon, a victory which made his jockey Joseph O'Brien the youngest winner in Breeders' Cup history, and as recently as March he landed the Dubai Sheema Classic at Meydan.
St Nicholas Abbey won close to £5million in win and place prize money having won nine of his 21 races.
He will undoubtedly leave a huge whole to fill at Ballydoyle.