Paul Mulrennan is set for a lengthy spell on the sidelines after suffering multiple fractures in his back after a fall on the gallops.
The leading northern rider took a tumble while riding out for Michael Dods on Saturday morning and subsequent X-rays revealed the extent of the damage.
Mulrennan’s agent, Richard Hale, said: “He had the X-rays and it’s not good news, unfortunately. It looks like he’s fractured three vertebrae.
“The last I heard it doesn’t sound like they’re going to operate, but he will obviously be immobilised for a while.”
Mulrennan had been due to ride top weight Master The World in the feature John Smith’s Cup at York on Saturday. He was replaced by Dane O’Neill.