Kieren Fallon will not be riding today, following a heavy fall at Royal Ascot on Wednesday.
The champion jockey, who had ridden a double earlier in the day, was the worst sufferer in the accident which took place during the Ascot Stakes.
He was taken under police escort to the Wexham Park Hospital near Slough after suffering an injury to his left shoulder and was detained there overnight.
Fallon had six booked rides at the Royal meeting this afternoon.
David Harrison will ride Arctic Owl for James Fanshawe in the Gold Cup, Richard Hughes will replace Fallon on The Queen's Interlude in the opening Ribblesdale Stakes and Michael Kinane takes over on Cover Up in the King George V Stakes.
Wednesday's incident was sparked off when Prairie Falcon slipped as the field approached the home bend.
Generosa and Natural Eight were also brought down in the ensuing melee.
Michael Hills, the rider of Prairie Falcon, and Natural Eight's jockey Alan Daly both hurt their knees.
Seamus Heffernan, the rider of Generosa, was unhurt and all four horses galloped past the post apparently unscathed by the ordeal.
Fallon was due to ride Kompliment for Alan Bailey in the Norfolk Stakes and Mark Johnston's Atlantic Rhapsody in the concluding Britannia Stakes. George Duffield takes the mount on Kompliment while Darryll Holland gets the leg up on Atlantic Rhapsody.
Newmarket trainer Jeremy Noseda has yet to find a replacement for Fallon on Sir Nicholas in the Cork And Orrery Stakes.
Holland has picked up another spare ride on Clipper in the Ribblesdale Stakes as Hills has also given up his rides today.
"I'm very stiff and sore this morning," Hills said. "The horse fell on its own and I landed on my knees - I think - it happened so quickly. I grazed both knees and then I got kicked on the calf and the arm.
"There's nothing broken but the leg is really swollen so I've got off today's, tomorrow's and possibly Saturday's as well.
"Obviously today is the worst day so I'm just playing it by ear but I'm looking to comeback on Sunday or Monday.
"I suppose I was lucky with that amount of runners."
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