Jockey Steve Drowne was taken to hospital after Nunthorpe Stakes heroine Jwala fell fatally in the Hong Kong Sprint at Sha Tin.
The jockey has also been reported to have suffered a punctured lung in the incident, which saw him stretchered from the track.
Jwala, trained in Newmarket by Robert Cowell, was in contention for a place a furlong out but was beginning to drop backwards when appearing to be squeezed between rivals and falling to the ground just 50 yards from the finish.
Cowell tweeted: "Thank you to everyone for their kind, sympathetic words. Jwala was a special racehorse - I am especially proud to have been part of her life."
Drowne only returned to race-riding after a year out in March this year, having lost his riding licence for 12 months when diagnosed with an enlarged heart after fainting from the effects of a virus. He had partnered 35 winners in the UK since that comeback, most notably the 40/1 victory of Jwala in York's Coolmore Nunthorpe Stakes.