Kauto Star has been rated as "50-50" for the Cheltenham Gold Cup after taking a fall when schooling last week.
Trainer Paul Nicholls revealed on his Betfair blog that the two-time winner took a tumble at his Ditcheat yard.
"There is no easy way to say this, but Kauto Star is only 50-50 to make the Cheltenham Gold Cup after a fall schooling," he said.
The Cheltenham Festival begins on Tuesday, March 13.
