Aidan O'Brien has confirmed US Army Ranger will miss Saturday's Dubai Duty Free Irish Derby due to an unsatisfactory scope.
The colt, who finished second to Harzand in the Investec Derby at Epsom earlier this month, had been backed into an odds-on favourite to reverse that form in the Curragh Classic.
However, following routine tests yesterday morning ahead of declarations for the race today, the Ballydoyle trainer has ruled US Army Ranger out of the race, leaving Ryan Moore to partner Epsom third Idaho as the stable's main hope.
The trainer told The Herald last night: "His scope just wasn't 100 per cent clean this morning. It is nothing serious but obviously we couldn't run him.
"We will have to give him a little rest now and we'll have a look at the second half of the season with him now. Obviously it is a big pity."
Idaho now becomes the main hope for Aidan O'Brien and he'll be ridden by Ryan Moore who has yet to win an Irish Derby. "Idaho is in good form and we'll look forward to running him. He has form on both (good and soft) types of ground but you would have to imagine the better the ground that the better he would be."
Trainer Dermot Weld had earlier in the week admitted that he would prefer the Irish Derby to be coming a week later to give Harzand more time to get over his "tough race" at Epsom but he will top this morning's declarations for the €1,500,000 contest. Weld had no further update last night and he said: "Providing nothing unforeseen happens he'll be declared and fingers crossed ahead of Saturday. At the moment there is nothing further to be said that hasn't already."
Harzand is now the 5/4 favourite with bookmakers BoyleSports and yesterday evening they were best priced 6/4 about Idaho although some firms had the O'Brien runner heading the market ahead of the Epsom Derby winner.
On the Betfair Sportsbook, Idaho is 5/4 with Harzand 11/8.
Jim Bolger, who won the race in 2013 with Trading Leather, is likely to be represented by both Moonlight Magic and Stellar Mass.
Moonlight Magic won the Derrinstown Derby Trial at Leopardstown but was disappointing at Epsom and Bolger is hoping for a truer showing at the Curragh.
"Moonlight Magic is very well," Bolger told The Herald last night.
"I would be hoping he would give a good account and that the Curragh would suit him better than Epsom.
"It is possible he just had an off day at Epsom but the track may have played a big factor," he added.
Ed Dunlop's Red Verdon will be the sole British-trained representative in the race and is now the third favourite. Champion jockey Silvestre de Sousa will again be onboard the colt who endured a luckless path at Epsom but still caught the eye of many when finishing sixth.
He was a supplemented entry on Tuesday at a cost of €100,000 to connections.