The Irish Derby and Champion Stakes winner is expected to be ridden by John Velazquez in the 10-furlong dirt race, in which he will clash with Preakness hero Bernardini, who runs in the colours of Sheikh Mohammed.
“He is already there and he seems to be fine,” said O’Brien. “He runs in the Jockey Club Gold Cup, which will be his first run on a dirt surface. We will see how he gets on there and how he is afterwards before making any decision about the Breeders’ Cup.”
Dylan Thomas, who beat Ouija Board at Leopardstown last month, is a 10-1 shot with Coral for the Breeders’ Cup Classic at Churchill Downs on November 4, with Bernardini the 6-4 favourite.
The Classic was nominated by O’Brien as the colt’s likely end-of-season target after his Irish Champion Stakes win, although Hills offer 8-1 about him for the Breeders’ Cup Turf.
O’Brien’s leading two-year-old Holy Roman Emperor may have run his final race of 2006 when landing last weekend’s Prix Jean-Luc Lagardere in Longchamp.
O’Brien added: “He is a possible for the Dewhurst (on Saturday week), but only a possible as he has had several quite quick races.”
Meanwhile, Speciosa is to have a bone scan to try to find the cause of her mystery lameness.
The 1000 Guineas winner is still suffering from the setback which caused her to be a late withdrawal from Newmarket’s Sun Chariot Stakes.
“She is still lame behind. It is a slight worry because they can’t find out what it is exactly,” trainer Pam Sly told At The Races.
“She was a little bit stiff on the Friday evening and then on Saturday morning she was lame. That’s unusual as she’s been as sound as a pound all this time.
“She’s having a bone scan and that will tell us if there is anything wrong in any bone, hock or joint.
“She went to the vets on Tuesday and he was hoping it was some soft tissue but he didn’t really find anything.
“The physio came this morning and she couldn’t find any soft tissue which was a worry, so I’m concerned.”