So You Think has been officially retired to stud and will return to Australia for the southern hemisphere breeding season.
The 10-time Group One winner was found to have pulled a muscle in his hind quarter forcing him out of this weekend's Eclipse Stakes which was to be his last race.
Managing owner Coolmore Stud said he would enter quarantine on Saturday.
"It's a big disappointment that he'll miss the Eclipse, but he's had a wonderful racing career and now it's time for him to shine at stud," Coolmore Australia's Tom Magnier said.
Formerly trained in Australia by Bart Cummings for whom he won two Cox Plates, the giant So You Think moved to trainer Aidan O'Brien's Tipperary base after Coolmore bought a controlling interest in late 2010.
He was to add five Group One successes to his resume including last year's Eclipse in O'Brien's care to go with the five he claimed in Australia.
So You Think had been in outstanding form this season with consecutive Group One victories in the Tattersall's Gold Cup at the Curragh and the Prince of Wales's Stakes at Royal Ascot.
"So You Think is an extraordinary horse and it was a real privilege to have had him here at Ballydoyle on loan from Australia," trainer Aidan O'Brien said.
So You Think will stand for $66,000 in his first season