Henry Cecil has admitted Frankel will be heading into the unknown in Saturday's Qipco Champion Stakes if the ground turns heavy.
Ascot has been hit by consistent rain in the build up to Champions Day and following another five millimetres on Wednesday night, clerk of the course Chris Stickels has mentioned the possibility of further rain on already soft ground.
The forecast for Saturday itself is better but with showers still forecast, the ground is unlikely to be any better than soft.
Frankel risks his perfect 13 from 13 record at the weekend but not since he made his debut has he raced on ground worse than good to soft.
Cecil has no worries if the ground were to stay as it is, but he would be slightly nervous about how he would perform on anything worse.
"I'm pretty confident he will be fine in soft ground but if it's heavy, we are in no man's land," said Cecil.
"He has never encountered it and with his action and turn of foot, I cannot be sure he would appreciate it."
The 10-furlong Group One is expected to be the four-year-old's final start before he retires to stud.
He completed two routine canters on the Warren Hill gallop in Newmarket on Thursday morning, with plenty of spectators on hand to watch his spin with regular work partner Bullet Train.
Cecil said: "I could not be happier with him. He seems full of himself."
"I'm pretty confident he will be fine in soft ground but if it's heavy, we are in no man's land," - Henry Cecil
Frankel will face just five rivals, headed by last year's winner Cirrus Des Aigles, who is likely to relish the testing conditions.
John Gosden's Eclipse winner Nathaniel is another who likes to get his toe in and he remains the horse to have got closest to Frankel when beaten just half a length on their respective debuts at Newmarket in 2010.
The German Derby winner Pastorius is another new rival for Frankel while Master Of Hounds will have his second run for William Haggas having won in Turkey on his first start for his new trainer.
Frankel's stablemate and three-parts brother Bullet Train is there to ensure a decent gallop.
Aidan O'Brien will not be represented having taken out Declaration Of War while Prix de l'Opera winner Ridasiyna also bypasses the race.