The high-class three-year-old is still in line to make an appearance in the Irish Champion Stakes on Saturday week, providing the ground is suitable.
He has missed intended outings in the Sussex Stakes and the Juddmonte International due to ground which was deemed to be too soft.
Should he not appear at Leopardstown, Gleneagles will have the Queen Elizabeth II Stakes at Ascot on Champions Day as a back-up on October 17.
A mouthwatering duel with American Pharoah, who only finished second in the Travers Stakes at Saratoga on Saturday, could then be on the cards if Bob Baffert’s colt stays in training.
O’Brien said: “Given suitable ground, Gleneagles will run in the Irish Champion Stakes on Saturday week and, failing that, he will be aimed at the Queen Elizabeth II Stakes at Ascot in October.
“His end-of-season target is the Breeders’ Cup Classic at Keeneland where he may face American Pharoah.”
Gleneagles has proved himself the best of his generation over a mile with Classic wins at Newmarket and the Curragh supplemented by his St James’s Palace Stakes victory at Royal Ascot.
He was declared to take on the Derby winner Golden Horn over 10 furlongs at York in the Juddmonte International, but O’Brien felt the ground had too much give in it after walking the track.
The Irish Champion Stakes is also over a mile and a quarter, but if the ground goes against him again it would mean Gleneagles could have to tackle a new trip, and an alien surface in dirt, at Keeneland.
O’Brien’s inmate was given an 8-1 quote by Paddy Power for the Classic on October 31, behind Beholder at 10/3 and American Pharoah, to whom Coolmore now have the breeding rights, at 7/2.
Before that Gleneagles could clash with Cirrus Des Aigles at Leopardstown on September 12 as the popular veteran is on course to make his comeback from injury.
The nine-year-old has not been seen since finishing last of four behind Solow in the Prix d’Ispahan in May on ground that was quicker than ideal.
He had earlier beaten Al Kazeem in the Prix Ganay — a 22nd career victory and his seventh success at the highest level.
After his first trip to Ireland, a return to Ascot is on the cards for what will be his fifth appearance in the Champion Stakes, a race he won in 2011 and then made Frankel pull out all the stops a year later.
“He’s on target for Leopardstown,” said trainer Corine Barande-Barbe.
“It will be his first run in Ireland — he likes going to new places.
“His problem wasn’t serious and given the way the ground has been, he hasn’t missed anything.
“He’s been in cracking form recently and we hope it rains a little. It’s not that he needs mud, it’s just that a few of his opponents don’t like it soft.”
Meanwhile, Richard Hannon’s Great Page is bound for the Moyglare Stud Stakes at the Curragh on Sunday week.
The daughter of Roderic O’Connor has already tasted victory in Ireland, having landed a Listed prized at Naas at the start of June, and is set to return as a contender for Group One honours following a recent success in Deauville.
Connections are hoping for testing conditions on the second day of Longines Irish Champions Weekend.
Tom Palin, representing owners Middleham Park Racing, said: “The plan would be to go to the Moyglare with Great Page, although she is also in the Prix Marcel Boussac.
“She is tough and would run through a brick wall for you. Soft ground is definitely the key to her.”