Aidan O'Brien has admitted he has doubts about ante-post favourite Frozen Fire's ability to see out the trip in Saturday's Ladbrokes St Leger at Doncaster.
The Irish Derby winner will be stepping into the unknown if the tackles the one-mile-six-furlong trip in the final Classic of the season on Town Moor.
He is one of eight possible runners for O'Brien along with Alessandro Volta, Bashkirov, Hindu Kush, King Of Westphalia, New Zealand, Washington Irving and William Hogarth.
Although the Ballydoyle team have yet to firm up their plans, the Leger is certainly looming large on Frozen Fire's agenda.
O'Brien said: "It is a great race and one of the most prestigious of the season so we are delighted to have horses to run in it every year.
"I am not sure of plans yet as we will have to wait and see what the weather does, but Frozen Fire is a strong possible at the moment.
"Alessandro Volta, Washington Irving, Hindu Kush and Bashkirov are all very strong possibles at the moment too, but they all have work to do.
"We are always concerned about the ground getting extreme.
"Frozen Fire is obviously a very classy horse which he showed when winning the Irish Derby, and we are not sure about the mile and six furlongs but we are hoping."
Frozen Fire currently heads the sponsor's market at 9-4 with Ralph Beckett's Oaks heroine Look Here next best at 4-1 as she makes her return from a long lay-off.
Andrew Balding hit the bar with third-placed Phoenix Reach in 2003 and he sends out German Derby third Top Lock this time.
The Nayef colt was given a break following his Hamburg trip and returned to action with a creditable second behind Centennial in the rescheduled Great Voltigeur at Goodwood last month.
"Top Lock ran in the German Derby and there was a lot of rain before the race to turn the ground soft and that was a concern, but he handled it very well," said Balding.
"He was third at Royal Ascot behind Campanologist and he ran well that day.
"We gave him a break after the German Derby, so he needed the run in the Great Voltigeur and I'm hopeful of a good run at the weekend.
"Until he ran in the German Derby I had doubts about him staying a mile and six but the more I see of him, the more confident I am that he will stay."
Balding knows Top Lock, who is a 12-1 chance with the sponsors, will be lining up in a classy renewal.
"It looks a very good race with Ralph's filly (Look Here) as she looked good at Epsom and watching the Irish Derby winner again, I can appreciate his turn of foot and you have Doctor Fremantle and Conduit as well," he added.
Sir Michael Stoute could field 33-1 shot Warringah as well as Doctor Fremantle and Conduit as he seeks a first Leger success.