Longchamp has the potential to be turned into its sternest test by the time the gates open for Enable's attempt at Qatar Prix de l'Arc de Triomphe history on Sunday afternoon, as conditions threaten to be as deep as the years of Solemia in 2012 and Montjeu in 1999.
France Galop's director of racecourses Matthieu Vincent warned on Thursday that persistent rainfall forecast from Friday onwards could quickly turn the current very soft ground to holding or heavy.
While Enable won the first of her Arcs at Chantilly on soft ground, she appeared to be outstayed by Waldgeist in more testing conditions last year. Despite winning an Oaks and two of her three King Georges in bad weather, Khalid Abdullah's star has never raced in Britain on anything officially worse than good to soft.
"We have an autumnal forecast with a weather front coming in from the west which is beginning to make its presence felt this morning," said Vincent. "We've had 20 millimetres of rain over the last five days and 3mm in the last 24 hours.
"We have somewhere between four and eight millimetres every day from Friday through Sunday, which might be the best of the three days."
The current very soft conditions have remained virtually unchanged since Monday but Vincent expects the going to slow once the rain arrives on Friday.
"The rail is out 17 metres for Saturday and this morning the track was measured at 4.1 or very soft on that line, while it is 4.0 back on the inner where we will race on Sunday.
"The likely going for Sunday is obviously dependent on exactly how much rain we get, but I think we will quite quickly get to a stage where it's holding or even heavy."
One of France's main challengers is expected to be Persian King, who will make what is expected to be his final career start before heading to stud at the Haras d'Etreham in Normandy.
Already a three-time Group 1 winner, Persian King will attempt to earn Andre Fabre a record-extending ninth Arc, while Pierre-Charles Boudot will aim for back-to-back successes after the 2019 triumph of Waldgeist.
While Persian King undoubtedly possesses the requisite class, he will be tackling a mile and a half for the first time, while he failed to give his running in testing conditions at Deauville in the Prix Jacques le Marois in August.
But Boudot, who dominated the entire meeting 12 months ago, is excited by the chance to bid for Arc glory on the son of Kingman.
"It's true that this year he has run over a mile and at the intermediate trip of the Prix d’Ispahan [1m1f], but there's enough encouragement in his pedigree to allow us to think he might stay," said Boudot.
"It's a gamble but it's pretty exciting as he's a horse with great quality."
Asked about Persian King's apparent inability to handle deep ground in the Marois, Boudot said he felt his mount was in better shape now than when finishing a distant fourth to Palace Pier.
"That day the conditions were really extreme," said Boudot. "After that he ran so much better in the Prix du Moulin and was much fitter that day, showing a totally different side to himself. The horse seems well on the gallops and he heads to the Arc in really good condition."
Boudot won the Juddmonte Grand Prix de Paris for Aidan O'Brien on Mogul, who will now be the mount of Ryan Moore in the absence of Love.
He told French racing channel Equidia: "Enable looks the one at this stage and whatever beats her will certainly win. Mogul made a very good impression last time but the ground has changed a lot since then.
"Stradivarius is a top stayer and very tough, so I see him as perhaps second or third and overall, it looks an Arc with a lot of good horses ahead of time."