Aidan O'Brien has been forced to juggle plans for Mother Earth after Santa Barbara met with a setback.
The 1000 Guineas winner was due to head to Australia to take in the valuable Golden Eagle next month, however, she is now set to run in America instead.
Santa Barbara had won two Grade Ones on her last two outings in the States, the Belmont Oaks and the Beverly D Stakes, and would have been a strong fancy for many at the Breeders' Cup.
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Now it seems Mother Earth, who has also won the Prix Rothschild this season and was unlucky in the Matron Stakes last time out, could take her place. Mother Earth is also still a possibility for the Sun Chariot at Newmarket before heading off on her travels.
"Unfortunately Santa Barbara has had a setback," said O'Brien.
"It doesn't look at the moment as if she's going to make the Breeders' Cup.
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"We've now rerouted Mother Earth. She was going to go to Australia, but we're thinking she'll be going to America to take in some of the races that Santa Barbara could have run in.
"It's a shame for Santa Barbara, she'd been going really well of late."