Apprentice Rossa Ryan was taken to hospital for precautionary tests following a nasty fall at Chester.
The 7lb claimer was unshipped when his mount Penny Red slipped up over two furlongs out in the ANS Maiden Fillies' Stakes.
He was reported to have lost consciousness straight after the tumble, but was conscious again before been driven by ambulance for further treatment.
"He was knocked unconscious. He regained consciousness while at the racecourse. He's been taken to the Countess of Chester for further precautionary tests," said clerk of the course Andrew Morris.
The stewards inquired into the incident and found that it was accidental and due to the filly "taking a false step which caused her to stumble and fall".
The following race was delayed by 12 minutes until all the emergency services were back in place.