Coolmore and trainer Aidan O'Brien took a chance by entering only Rip Van Winkle in the Breeders' Cup Classic, despite the colt's history of foot problems. They now could wind up without a horse in the race if Rip's most recent setback proves serious enough to force his withdrawal.

O'Brien told the Racing Post Tuesday, "This horse has had no clean run this year and he hasn't had one this time. The problem is again a foot problem but this time a different foot is affected."

Rip Van Winkle is the overwhelming 6-4 favorite with William Hill and Coral. O'Brien said Rip Van Winkle will go to the track on Wednesday, after which they will determine the extent of the injury.

"With Rip Van Winkle it's always been day by day," O'Brien said. "What he's done up to now I've been amazed that he's been able to do