Coneygree has been ruled out of the Boxing Day King George VI Chase because of injury.
The horse, who won the Cheltenham Gold Cup in March, is expected to miss the entire festive period, with his return to come at some point next year.
"Coneygree won't run in the King George having sustained a new injury. He's being assessed by vets this morning," Sara Bradstock, wife of trainer Mark, told the Racing Post.
Fitness problems also prevented the eight-year-old from racing in the Hennessy Gold Cup at Newbury last month.