Timmy Murphy was ruled out of Saturday's Hennessy Gold Cup at Newbury after it was confirmed he had broken two vertebrae in a fall on Friday.
The Irishman was due to ride trainer David Pipe's The Package in the prestigious showpiece at the Berkshire race track.
Murphy suffered a heavy fall at Newbury when partnering Leeroar Inkerman in the final race of the day and was immediately taken to hospital for X-rays.
And he tweeted, following his accident at the third flight, "two broken vertebrae for my troubles but, hey, still walking."
He is likely to be out of action for six weeks, while Tom Scudamore took over Murphy's mount in the Hennessy.