Frankie Dettori has been ruled out for the season after he fractured his right ankle at Nottingham on Wednesday, the jockey's business manager Peter Burrell told Press Association Sport.
The Italian jockey was unshipped from Eland Ally prior to the 32Red.com Handicap and was stood down for the rest of the day.
Although an initial on-course prognosis suggested he had suffered only soft-tissue damage, X-rays subsequently revealed a break.
Dettori was due to partner leading Prix de l'Arc de Triomphe fancy Treve at Longchamp on Sunday.
Burrell told Press Association Sport: "It's bad news, not good news.
"He went to Cambridge Hospital and X-rays found that he had suffered a fractured ankle.
"He was extremely disappointed on the phone and did not want to discuss it much more than that.
"It's an extremely painful injury. Sunday is out - as is the season."