Leading British jockey Frankie Dettori has delayed his riding comeback from a broken collarbone by three weeks, while the favorite to succeed him as champion jockey, Robert Winston, has been sidelined for the rest of the season with a broken jaw. Dettori had hoped to return to partner Dubawi in the Prix du Haras de Fresnay-le-Buffard Jacques le Marois (Fr-I) at Deauville on August 14 but, in his contracted column in The Times, admitted he is nowhere near ready. "I had set my heart on it, but I cannot even sit on a horse yet," he said. "On Saturday (Aug. 6) I jumped up on an old horse I have at home, and I found that very hard. I was in so much pain the next morning that I had to go back on the painkillers."Dettori suffered his injury in a fall at Sandown more than five weeks ago (July 2) He recently returned from a two-week break in Sardinia. Meanwhile Winston -- widely tipped as the eventual successor to Kieren Fallon as Sir Michael Stoute's retained rider -- broke his jaw in several places in a fall at Ayr Aug. 6. The final two races of the evening meeting were abandoned as a result. Winston had partnered 98 winners until then and looked odds on to land the jockeys' title. Jamie Spencer, back riding as a free-lance after a year riding for Aidan O'Brien, is now favored to take the title instead.