Ryan Hatch misses out on the plum ride on The New One in the StanJames.com International Hurdle at Cheltenham on Saturday after being hurt in a fall there on Friday.
Champion jockey Richard Johnson now takes the mount on the Nigel Twiston-Davies-trained gelding, who is seeking a third win in the Grade Two contest.
Hatch was taken to hospital for assessment on a possible sternum injury following a tumble from Cogry in the Unicoin Group Handicap Chase.
Twiston-Davies' assistant Carl Llewellyn said: "At the moment, they are looking at possible damage to his sternum.
"He was originally going to Gloucestershire Royal, but he's now on his way to Bristol.
"I don't know much more than that, whether it is bruising or something else."
It is bad luck on Hatch as he would have partnered The New One on what should have been his chasing debut at Exeter a week ago, only for the meeting to be abandoned.
It was only then Twiston-Davies decided on a change of plan for The New One, who has been successful five times in total at Cheltenham and was fourth to Annie Power in the Champion Hurdle in March.