Cheltenham Gold Cup hero Minella Indo has been ruled out of the Ladbrokes Punchestown Gold Cup on Wednesday with a bruised foot.
Henry de Bromhead was forced to pull the plug on his intended seasonal swansong when he discovered the problem on Monday.
Minella Indo led home a historic one-two for the trainer in the Gold Cup last month, when beating stablemate A Plus Tard.
"It's a very minor thing, but it's the right thing to do and we thought we'd let everybody know sooner rather than later," said De Bromhead.
"He just didn't seem right when we were looking at him and when we had a look he's bruised the sole of his foot.
"We'll call it a day now, he's had a great season."
Minella Indo's win capped a fantastic Cheltenham for the De Bromhead team, having also won the Champion Hurdle with Honeysuckle and the Champion Chase with Put The Kettle On - the first time all three feature races had been won by the same trainer in one year.
De Bromhead then went on to saddle the first two home in the Grand National with Rachael Blackmore creating history on Minella Times, beating Balko Des Flos.
In the absence of Minella Indo, Al Boum Photo, who had won the previous two Gold Cups at Cheltenham and was third this year, is the new 13-8 favourite with Coral.
"Not much has gone wrong for Henry de Bromhead in recent weeks, but the setback to Minella Indo means the trainer won't be adding the Ladbrokes Punchestown Gold Cup to his incredible big-race haul this season," said Coral's David Stevens.
A field of six will now line up, including a four-pronged challenge from the Willie Mullins stable, with last year's winner Kemboy, Easy Game and Melon joining Al Boum Photo.
Paul Nicholls sends over Clan Des Obeaux, winner of the Betway Bowl at Aintree this month, while Joseph O'Brien's Fakir D'oudairies is the other contender.
Cheltenham Festival winners Galopin Des Champs and Vanillier clash in the Irish Mirror Novice Hurdle.
The latter lifted the Albert Bartlett Novices' Hurdle for Gavin Cromwell, while the Mullins-trained Galopin Des Champs took the Martin Pipe Conditional Jockeys' Handicap Hurdle.
Mullins also has Albert Bartlett fourth Stattler - with the third, John McConnell's Streets Of Doyen, also in the mix in an eight-runner field.
Sir Gerhard, for the Mullins stable, is the headline act in the third Grade One race on the card, the ITM - Supporting Irish Store Sales Champion INH Flat Race.
The six-year-old attempts to take his perfect record under Rules to four after his success in the Weatherbys Champion Bumper at Cheltenham.
He got the better of stable companion Kilcruit by half a length that day, and the pair clash again in a mouth-watering contest.
Mick Halford's Ardla, Eric Bloodaxe from Joseph O'Brien's yard and Stuart Crawford's O'Toole are also among the eight runners.