Trainer Michael Stoute believes Hillstar's fondness for soft ground could stand him in good stead for the Qipco Champion Stakes at Ascot on Saturday.
The Royal Ascot-winning colt broke his maiden in a Leicester bog last October and has since gone on to finish third in the King George VI And Queen Elizabeth Stakes in July.
Hillstar, who was last seen finishing fourth in a fast-ground Juddmonte International Stakes at York, will be out to give Stoute a third triumph in the Champion Stakes.
The Newmarket handler told the Telegraph: "I've been very happy with his work and we know he likes the ground.
"I feel he could well improve again with more juice in the ground.
"It was certainly quick enough for him in the King George."
French trainer Corine Barande-Barbe said Cirrus Des Aigles, who is again set to be ridden by Christophe Soumillon, is "just perfect".
The seven-year-old gelding won the Champion Stakes two years ago before giving Frankel one of his sternest tests in the race 12 months ago.
Although he made a subdued start to the campaign, Cirrus Des Aigles responded with easy victories at Maisons-Laffitte and in the Prix Dollar at Longchamp on Arc weekend.
Barande-Barbe told the Guardian: "You must always respect the opposition, but I think he might win.
"He's very well, just perfect. I think he's on his way to the top.
"I had never doubted him, but you never know.
"He is getting a bit older but finally he is just the same as he was last year and the year before."