Aidan O'Brien looks set to rely solely on Granddukeoftuscany in the Ladbrokes St Leger at Doncaster on Saturday.
The Ballydoyle trainer has won the final Classic of the season four times, most recently with Leading Light 12 months ago.
O'Brien has also left in Irish Derby runner-up Kingfisher but seems likely to run the lightly-raced Granddukeoftuscany, the winner of a Tipperary maiden on his second start and fifth in the Great Voltigeur at York last month.
Kingfisher is instead set to join illustrious stablemate Australia in the Irish Champion Stakes on Saturday night.
"Probably only Granddukeoftuscany will run, with Kingfisher going to Leopardstown" - Aidan O'Brien
O'Brien said: "Probably only Granddukeoftuscany will run, with Kingfisher going to Leopardstown."
Asked if Joseph O'Brien would ride, O'Brien said: "I doubt it."
Scorpion (2005), Brian Boru (2003) and Milan (2001) are O'Brien's other Leger winners.
Granddukeoftuscany is a 20-1 chance with the sponsors.
James Doyle is poised to pick Voltigeur second Snow Sky over Kings Fete from Michael Stoute's two contenders.
Teddy Grimthorpe, racing manager to owner Khalid Abdullah, said: "James Doyle will have the choice and I'd imagine he'll go for Snow Sky, hopefully Ryan Moore will ride the other one."
Ante-post favourite Kingston Hill featured among 15 horse left in the world's oldest Classic at the five-day confirmation stage.
Ladbrokes admit the market centres around Roger Varian's classy colt, who won the Racing Post Trophy at Doncaster last autumn.
Spokesman David Williams said: "The entire shape of the race seems to hinge on the participation of Kingston Hill.
"The 14mm of rain over the weekend would seem to be a big boost for his followers with more watering expected this week."
Ladbrokes have Kingston Hill as their 5-2 market leader, with Snow Sky clear second-best at 5-1 ahead of John Gosden's Romsdal and Richard Hannon's Windshear, both at 8s.
As well as Derby third Romsdal, Gosden has two other possibles in March Stakes winner Forever Now and Marzocco as he too chases a fifth win in the race.
After opening his Leger account with Shantou in 1996, the Newmarket trainer has taken the race a further three times in recent years with Lucarno (2007), Arctic Cosmos (2010) and Masked Marvel (2011).
The Leger has so far eluded Mark Johnston, but the Middleham trainer has three horses with sound claims this year in Queen's Vase scorer Hartnell, March Stakes runner-up Alex My Boy and Eclipse third Somewhat.
Completing the list are Scotland, Min Alemarat and Odeon.
