Enable bids to become the first horse to win the Prix de L'Arc de Triomphe three times on Sunday, boosted by the shock withdrawal of Aidan O'Brien's four runners.
Frankie Dettori and Enable will now face just 10 rivals with the rain-affected ground at Longchamp racecourse the main obstacle to her making history.
O'Brien withdrew his quartet -- which included the fancied Mogul and Epsom Derby champion Serpentine -- late on Saturday after they tested positive for a banned substance.
It is believed the substance may have been in contaminated horse feed. Leading English trainer Roger Varian withdrew all seven runners he had racing in England on Saturday due to using the same feed.
Various batches of Gain Equine Nutrition feeds have been found to be contaminated with a prohibited substance.
"Unfortunately the results of the urine samples taken from the horses yesterday have come back positive from the French laboratory," read a tweet from O'Brien's Ballydoyle Stables account.
"There is a possibility that the contaminant may have left their system by the time of racing tomorrow.
"However we have no guarantee of this, and in order to protect the integrity of racing we have decided to withdraw all our horses from racing tomorrow (Sunday)."
Enable may be unaffected by the feed furore but the heavy rain throughout the week in Paris has turned the ground at Longchamp into a real challenge for her.
Dettori described the going as "heavy" after riding there on Saturday with fellow jockey Christophe Soumillon going further and saying it was the "most gruelling" he had ever experienced at the track.
- 'A very calm horse' -
Enable's trainer John Gosden mused it was "Nature's way of getting back at us (humans)" after years of neglecting it.
The 69-year-old Englishman, who along with Dettori is bidding for their fourth win in six editions of the Arc, fears the race is going to turn into a grim test of endurance.
"She (Enable) doesn't much like that ground. She prefers the easy side of good, so she can show her class, but it is going to be a bit of a slog," said Gosden.
"It is drying up now and it is tacky, but you might get another shower or two.
"It is Longchamp, by the River Seine -– it is deep."
Enable would not have been running but for seeing her hopes of a third successive Arc triumph last year dashed when runner-up having been collared by Waldgeist in the dying strides.
"I think Prince Khalid (Abdullah her owner and breeder) was brave in saying we'll try again," Gosden told English broadcaster ITV.
"We're here and we're trying. We care about the filly in every way, she's a gorgeous filly to be around and she's been with us for five years.
"Let's hope she gets a great run round -– and if she wins, marvellous, if she doesn't, she couldn’t have done more for racing.
"She reminds me of the great jumping legends who had tremendous popular appeal Denman, Arkle, Desert Orchids –- she’s that kind of feeling."
Gosden is two-handed as he runs his legendary three-time Ascot Gold Cup winner Stradivarius but he dislikes the 'bottomless ground' even more than Enable.
Winning the Arc has been the dream of Japanese turfistes for decades but their one runner Deirdre has been in poor form this year.
Enable's greatest dangers appear to be the Jean Claude Rouget-trained duo Sotsass and Raabihah and Francis-Henri Graffard's German Derby winner In Swoop.
Graffard says those who back In Swoop should not be unduly alarmed if he is trailing behind the other runners early on.
"He's by nature a very calm horse, which can almost give the impression that he’s not engaged mentally in his race," said Graffard.
"He only really hit full stride in the final 200 metres of the race (the German Derby) before going on to win."