Paul Hanagan faces a spell on the sidelines after suffering a hairline fracture in an arm following a fall at Goodwood on Tuesday.
Hanagan's injury is in his lower left arm and occurred when his mount, the Ed Dunlop-trained White Nile, slipped up in the bet365 Summer Stakes.
The former champion jockey had been enjoying a stellar season after winning the Investec Oaks and the King George VII And Queen Elizabeth Stakes on Taghrooda, as well as the Coral-Eclipse aboard Mukhadram.
Those three Group One wins came in the colours of his boss, Sheikh Hamdan Al Maktoum.
Hanagan will, however, be hoping to be back in action towards the end of August, when Taghrooda is due to run in the Darley Yorkshire Oaks.
Sheikh Hamdan's racing manager Angus Gold said: "I haven't actually spoken to Paul but I have been told that there is a crack in there somewhere.
"It's obviously a blow. Things had been going well, but these things happen in racing."