Jason Maguire will miss the Cheltenham Festival after he suffered a fractured sternum and bleeding on his liver in a fall at Stratford on Monday.
The Grand National-winning jockey rode the John Quinn-trained Scots Gaelic in a two-mile handicap hurdle when he was unseated at the second flight and was kicked in the stomach by another horse.
Maguire was airlifted to University Hospital Coventry, where X-rays revealed significant damage.
Niall Hannity, a friend of Maguire, said from the hospital on Monday evening: "He has fractured his sternum and he's got bleeding on his liver.
"He's definitely out of Cheltenham and his wife, Lauren, is with him."
Maguire was due to have three rides on the first day of the Festival on Tuesday, including Un Ace in the Sky Bet Supreme Novices' Hurdle.
Conditional jockey Ciaran McKee, who rode outsider Descaro for trainer John O'Shea in the same race in which Maguire was injured, fell at the third hurdle.
McKee was briefly knocked unconscious and was taken to the same hospital by road ambulance.
Stratford clerk of the course Stephen Lambert said: "Ciaran was unconscious for about three minutes."