Apprentice Luke Dittman has been taken to hospital for precautionary tests after falling at the Sunshine Coast on Monday.
Dittman on the favourite Eljetem and Rick McMahon on Atarartzi were dislodged near the 1000m mark in the Sunco Motors Maiden (1400m).
Red N Brown, ridden by Jim Byrne, also pulled out of the race after the incident.
Dittman had only picked up the ride on Eljetem as a late replacement for apprentice Matt McGuren.
He was reportedly unconscious when ambulancemen reached him, but regained consciousness before being placed on a stretcher.
Dittman suffered facial injuries and a possible collarbone injury.
McMahon was badly shaken but able to return to the enclosure, where he was examined by the club doctor.