Robert Thornton has been told he could be on the sidelines for three months with the broken arm he suffered in a fall at Hereford last Sunday.
Thornton needed to have an operation on the injury earlier this week and expert consultant Richard Keys has given him the bad news.
The jockey said on Twitter: "Mr Keys has just told me 3 months out. I could cry again. Still aiming for 6-7 weeks. I have something to prove again!"
Meanwhile, Nicky Henderson has ruled last year's runner-up Riverside Theatre out of the King George VI Chase at Kempton.
The seven-year-old has been sidelined with a stress fracture to his pelvis.
Sunday Indo Sport