Kingscliff has been ruled out of next Thursday's Cheltenham Gold Cup by trainer Robert Alner.
The seven-year-old had been second favourite, behind Henrietta Knight's Best Mate, for chasing's blue riband following wins at Ascot and Cheltenham.
"He doesn't run on Thursday as I am not happy with him," Alner told attheraces. "If it had been 14 days earlier it would have been all right. I jumped him 10 days ago and he was absolutely spectacular, he jumped like a rocket," Alner continued.
"I jumped him again yesterday and he just wasn't the same horse. He didn't jump that well and I just wasn't happy with him. You can pretend that he is fine but underneath we know that he is not 100 per cent."
Kingscliff earned rave reviews when running away with last year's Christie's Foxhunter Chase at the Festival and following two impressive victories earlier this season was overturned last time out at Haydock.
The gelding was beaten 13 lengths by Artic Jack in the Peter Marsh Chase but was subsequently found to have a muscular problem and has been receiving treatment from physiotherapist Mary Bromiley.
"It is probably a recurrence of the muscle problems he sustained at Haydock. He had been working really well, looks really well and is a happy horse but he just wasn't right," Alner said.
"Fortunately it isn't a leg problem or anything like that, and he is only seven, so there are plenty of other year's. But to run him when I am not confident that he is 100 per cent is no good to the horse, jockey, the public, myself and the owner.
"I did have a long chat with the owner and he said that if I wasn't happy we should just forget it, there is always next year.
"I doubt if there are any other races of him this season. There is Punchestown but he is a very big horse and you would be thinking that at this time of the year that the ground would be going against him so I am inclined to just draw a line through the season.
"Having said that, we'll just assess the situation and see how we go but he will not be running on Thursday."