Diamond Necklace and Benvenuto Cellini could join Minnie Hauk in the Prix de l'Arc de Triomphe at the beginning of October.
O'Brien's yard is littered with potential Longchamp candidates and it looks as if last year's runner-up Minnie Hauk will be joined by two stablemates in France this time around.
The daughter of Frankel was narrowly defeated by Daryz in the middle distance showpiece last year, continuing a fine year where she won the Oaks, Irish Oaks and Yorkshire Oaks. She hasn't quite been at the same level this season, however, winning just one of her five starts.
She was sent off as 5/2F for the Arc in 2025 but can be backed at 20/1 heading into next month.
Stablemate and Irish Derby winner Benvenuto Cellini, according to O'Brien, is also a possible for the race.
"Benvenuto Cellini goes to France for the Niel," O'Brien told the press during the Ballydoyle media day. "He could be a possible for the Arc if the ground was nice. If it wasn't, he'd go on to the Breeders' Cup, with Hong Kong in mind too."
His early season exploits were shrouded in controversy after he was deemed a non-runner after being sent off 3/1 favourite for the Derby. The Frankel colt got his leg caught in the stalls just before the race began; race day stewards seeing this as enough of a reason to void his run, despite him jumping from the stalls and eventually finishing 10th.
He backed up his subsequent Irish Derby win with a fine effort behind older rivals Kalpana and Calandagan in the King George VI Stakes at Ascot.
Now 16/1 for the Arc, he is the same price as fellow three-year-old and Arc possible Diamond Necklace.
"We ran Diamond Necklace back a bit quicker last time," he said. "We thought if we went to the Vermeille over a mile and a half and she had a hard race and then we decided to go to the Arc, it could come up a little quick for her," O'Brien said.
"It's possible that she could be trained for Arc weekend, for the Opera or the Arc. She'll have a good, long run-in to the race and we think she'll be tighter and fitter than at Deauville. Maybe I was trying to be a bit clever, as I thought she might be good enough to win at Deauville without being too hard on her."
O'Brien's star filly lost her unbeaten record last time out in the Prix Jean et Louis Romanet. Prior to her defeat to Aventure, the three-year-old had won French 1,000 Guineas and French Oaks, as well as the Nassau Stakes where she comfortably overturned Friendly Soul at Goodwood.
Any odds displayed were correct at the time of writing and are subject to fluctuation.
