Rebel Raider, a leading fancy for the Emirates Melbourne Cup on November 3, has been ruled out of the Flemington feature.
The Leon Macdonald-trained four-year-old suffered a leg injury earlier in the week and requires an operation.
Macdonald told The Age: “The vets tell me he’s a 70-30 chance of making a full recovery, but I think it’s better than that.
“Fingers are crossed that we’ll be here in 12 months with him as a five-year-old.”
Rebel Raider, who won the South Australian Derby in May, was as low as 12-1 to claim the Melbourne Cup.