Alistair Rawlinson faces a lengthy spell on the sidelines after breaking his ankle in a fall at Windsor on Monday evening.
Rawlinson also sustained four fractured ribs and a swollen hip in the incident about two furlongs out in the Fitzdares Sprint Series Handicap.
His mount Diligent Lady suffered a fatal fall, bringing down Centurion Song, ridden by George Buckell.
Both jockeys were treated on course before being taken to hospital for further assessment.
Rawlinson came out worse of the two. He rides for Rutland trainer Mick Appleby, who gave an update on his condition.
“I’ve spoken to him. He’s broken his ankle and he’s got four broken ribs. His hip is swollen and sore but he was quite lucky. It looked a bad fall,” said Appleby.
“I think he has to have an operation on his ankle to have some metalwork in it.
“He’ll be off for quite some time, I would think.”
Buckell appears to have escaped serious injury and is looking to be back in the saddle later this week.
“George is absolutely fine. He has a small bit of pain in his neck but X-rays were clear,” said his agent, Simon Dodds.
“He’s going to Oaksey House for some physio. He’s hoping to be back in action this week if he passes his medical.
“He wishes Ali all the best and hope he is OK.”