Quito De La Roque and Jessies Dream will both miss the Hennessy Gold Cup at Leopardstown on Sunday.
The former, 9-4 second-favourite with Paddy Power behind Quel Esprit after Jessies Dream had been ruled out earlier in the day, scoped badly this afternoon.
Quito De La Roque had last been seen finishing third to Synchronised in the Lexus Chase over Christmas.
His trainer Colm Murphy said: "He definitely won't run, he scoped badly. It's just a little hiccup really, we weren't 100 per cent happy with him when he was ridden this afternoon, so we had him scoped to see what the problem was and he has a bit of mucus in him.
"I'm not sure what we will do now, I'll speak to Michael and Eddie (O'Leary, of owners Gigginstown House Stud) - this was Plan A so I'm not sure what Plan B will be."
Prior to his run in the Lexus, the eight-year-old Quito De La Roque had beaten Sizing Europe in the JNWine.com Champion Chase at Down Royal in November.
Jessies Dream, meanwhile, could miss the rest of the season after failing to please trainer Gordon Elliott in his final piece of work ahead of the weekend.
The nine-year-old has not run since finishing second to Bostons Angel in the RSA Chase at Cheltenham in March.
Elliott said in his Betfair blog: "Following very disappointing display in his last piece of work before the Hennessy Jessies Dream will not run in Leopardstown on Sunday.
"As I said in yesterday's piece, he was in great form and schooled really well but today there was no sparkle so at this stage, with time against us, I'm not sure he will make the track at all this season."
