Opera Singer, one of the favourites for the Qipco 1,000 Guineas, is set to miss the fillies Classic due to “a little setback”.

The daughter of Justify finished last year as the best juvenile filly in Europe after winning the Group 1 Prix Marcel Boussac by five lengths and was as low as 4-1 for the Newmarket on May 5. But trainer Aidan O’Brien revealed she had missed two weeks of full training and her participation was “more unlikely than likely”.

Instead Brilliant, who gave Ballydole a winning start on the first day of the new Irish Flat Turf season at the Curragh by landing a Group 3, had earned a start at Newmarket instead.

O’Brien’s three-year-old team for 2024 include City Of Troy, hot favourite for both the 2,000 Guineas and Derby, and the also unbeaten Henry Longfellow.

“Opera Singer is a little bit behind them and might not make the English Guineas but the colts are good and forward and are where we want them to be,” the trainer told RacingTV. “She had a little setback and had to have two weeks easy and when you have two weeks easy it’s difficult to get to the English Guineas. It’s possible but I’d say more unlikely than likely.

“She could end up starting at the Curragh rather than starting in England. We won’t force her. She is a beautiful big filly.”

O’Brien confirmed City Of Troy would head to Newmarket with Henry Longfellow being aimed at the French 2,000 Guineas in a campaign that will go ahead without long serving rider Seamie Heffernan, who has turned freelance.

“Seamus must have been riding for us for 20 or 30 years, coming in six mornings a week,”said O’Brien.

“He felt he might like to give the outside world a bit of a chance."