Frankie Dettori sustained a sprained ankle at Nottingham before the start of a race.
The jockey, who is due to ride leading Prix de l'Arc de Triomphe contender Treve at Longchamp on Sunday, was unshipped from Eland Ally prior to the and was unable to put any weight on his right ankle as he attempted to get to his feet.
Dettori returned to the Nottingham medical room in a wheelchair and was stood down for the day.
Nottingham course doctor Chris Reynolds said the rider did not need to have an X-ray and that he should make a full recovery by the weekend.
He said: "It's a sprained ankle, a soft-tissue damage injury.
"No X-rays are needed but he has been stood down for the day.
"It normally takes a few days to recover from such an injury."
When asked if Dettori would be fit in time for the Arc, Reynolds said: "It's definitely a possibility."