Rizeena will miss the Etihad Airways Irish 1,000 Guineas at the Curragh on Sunday.
Clive Brittain's filly is denied a run in the Irish Classic after she suffered a setback at her Newmarket home on Thursday morning.
Brittain said: "It's heartbreaking, but it's what the game is all about. You have your good days, and you have your bad days."
He added: "She'd done all her major work six days ago, and was only having a blow-out. The girl who looks after her was very happy with her, as always.
"But an hour later, after the horse had a wash-down, we found a bit of blood coming out of her near-side nostril.
"It was only a trickle, but if there is in any doubt, we always take them out.
"It could be something over nothing, but you can't take any risks.
"The filly is still bright-eyed and alert. I don't think we've a sick animal on our hands."
Rizeena won the Group One Moyglare Stud Stakes on her last visit to the Curragh, but only finished seventh behind Miss France on her seasonal bow in the Newmarket Guineas.