No decision has been made yet on whether High Chaparral will defend his Breeders' Cup Turf title at Santa Anita later this month.
The Aidan O'Brien-trained four-year-old, who was third in the Prix de l'Arc de Triomphe last Sunday, won the mile and a half event at Arlington last year and a return was thought to be planned.
However, O'Brien has confirmed it is "uncertain" whether High Chaparral will head to California on October 25th.
He told the Racing Post: "High Chaparral seems to be fine, but it is far from certain that he will go to the Breeders' Cup. That decision has not been made yet.
"He ran a good race in the Arc. The only three times he has been beaten in his career he was racing right-handed."
Even if High Chaparral does not go to America, O'Brien has a strong team that could still run.
"Yesterday is a possible for the Filly & Mare Turf while Hold That Tiger will hopefully go for the Classic," he added.
"Grand Reward and Old Deuteronomy are possibles at this stage for the Juvenile while Statue Of Liberty may go for the Mile."