Group One scorers Alexandrova and Dylan Thomas will not be seen in action on the racecourse again this season.
Aidan O'Brien had considered taking the pair to the Breeders' Cup next month but has instead decided to retire them both for the year.
Having won the Oaks at Epsom in June, Alexandrova went on to land a hat-trick of top-tier successes by lifting the Irish and Yorkshire versions of the 12-furlong feature.
She was a well-held third behind Mandesha in the Prix de l'Opera at Longchamp last time, however, and O'Brien feels she will now benefit from a rest.
He said: 'Alexandrova never travelled in the Prix de l'Opera at any stage, and it just wasn't her for some reason. For a filly with a lot of speed that shouldn't have been the case, and she came back sore after France.
'She might have been feeling the effects of a long season, so we're going to leave her alone for this season, and she won't be travelling to America. We're hopefully going to look forward to next year with her,' he told the Racing Post.
Dylan Thomas enjoyed high-profile victories in the Irish Derby and Champion Stakes, but after failing to handle the dirt at Belmont Park last weekend, O'Brien has chosen not to ask the colt to compete again this season.
'Dylan Thomas didn't run his race in America last weekend on the dirt and may also be feeling the effects of a long season, so we've also decided to leave him at home,' he explained.