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 this weekend.
"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.