Seamie Heffernan will replace Johnny Murtagh, re-routed to France to partner Henrythenavigator, should Duke Of Marmalade face New Approach in today's rearranged Irish Champion Stakes at Leopardstown.
But the eagerly-awaited re-match between the two may not take place because of the testing going. "The instinct is not to run the Duke," said O'Brien, "but we will leave a final decision until the morning."
Derby winner New Approach has replaced Duke Of Marmalade as favourite today, but the meeting at the rain-lashed Co Dublin track must survive a 7.30 am inspection.
If it goes ahead Heffernan, who has already partnered Halfway To Heaven, Frozen Fire and Again to Group One wins in Coolmore's colours this year, is scheduled to renew his acquaintanceship with the first-named in the Matron Stakes.
At Longchamp, top miler Henrythenavigator will face 10 rivals, including French fillies Natagora, Goldikova and Darjina, in the day's other top-level contest, the Prix du Moulin.
The Haydock Sprint Cup, lost yesterday due to waterlogging, will now be run at Doncaster on Saturday. It will share the bill with the St Leger for which Oaks heroine Look Here, absent since her Epsom triumph, has been given the go-ahead. Eddie Ahern replaces injured Seb Sanders on the filly who is 5-1 second-favourite behind 2-1 shot Frozen Fire for the final Classic.