Star apprentice Matthew Chadwick was carried unconscious away from the 200m mark of the track, then rushed to hospital for tests before being cleared of any serious injury.
Chadwick was later diagnosed as having suffered only concussion but will be stood down for a mandatory five days after it was ascertained that he had lost consciousness, and he will miss Wednesday's meeting at Happy Valley. Chadwick was charging into a narrow gap on the heavily-backed $23 favourite when the opening slammed shut and he clipped the heels of Sleep Well.
Down went Gallant Champion, down went Chadwick and the jockeys championship front runner was left a sprawled rag in front of the packed main grandstands.
Attendants stretchered him off the track some minutes later.
Jockey Challenge betting, for which Chadwick was one of the strong favourites at that stage, was thrown into disarray as a number of his strongly-fancied mounts would suddenly not be included in the points score any longer.
'In the end, the news was as good as can be,' said racing director Bill Nader. 'Matthew seems fine, if a little groggy, but he has been cleared of any breaks or other serious damage,' he added.
He is expected to remain in hospital overnight for observation. An inquiry into the circumstances of the fall was later adjourned by the stipendiary stewards until Chadwick is available to give evidence. The race itself turned out to be an upset win for Almond Lee Yee-tat's Meridian Star, who rekindled the relationship between the trainer and jockey Gerald Mosse.
Lee has a long history with Mosse, who was stable rider for David Hayes when Lee was the Australian trainer's assistant for a number of years.
Mosse, in just his second ride since returning from France last week, was able to dictate the slow tempo on the seven-year-old, who improved sharply on his other four runs since surgery last February to release his trapped epiglottis.
'The throat thing hasn't bothered him,' said Lee. 'But he was just lucky today - he was able to go slow, with no pressure, and he kept running.'