Jockey Davy Russell has suffered a suspected broken arm and leg in a fall at Gowran Park in Ireland.
Russell, who won the 2014 Cheltenham Gold Cup on Lord Windermere, was hurt when his mount Feenakilmeedy came down.
Gowran clerk of the course Paddy Graffin said he was taken to hospital with suspected fractures to his humerus (upper arm) and tibia (lower leg).
Earlier on Saturday, the 35-year-old revealed he had lost the ride on Lord Windermere, trained by Jim Culloty.
Graffin said: "Basically it was Davy who brought down the other horse (Shuilamach) and he took the full brunt of a horse travelling at over 30 miles an hour."
Russell, who also won the 2013 RSA Chase at the Cheltenham Festival on Lord Windermere, said he was "very disappointed" to lose the ride after the horse was pulled up when defending his title on 13 March.
"I'll never forget last year's Gold Cup win on the horse which was one of the highlights of my career," Russell told the Irish Daily Star.
"After the (2015) Gold Cup, Jim told me he didn't want me riding his horses.
"He wasn't happy with the ride I gave the horse (Lord Windermere) and he said he wanted a change."