Irish jockey Eddie Creighton has been placed in an induced coma in hospital following a fall at Warrnambool racecourse on Saturday.
Creighton was riding in the meeting at the Victoria course when he was unseated from The Walrus, who stumbled soon after the start.
It was initially suspected that he had suffered a broken left arm and concussion, but his condition deteriorated at Warrnambool Base Hospital and he was subsequently transferred to The Alfred in Melbourne.
Racing Victoria said in a statement that his condition was "serious but stable".