Mark Coumbe was taken to hospital complaining of pelvic, back and leg pains following a fall at Southwell.
The 3lb claiming apprentice, who was out for eight months after fracturing four vertebrae in July 2008, suffered his latest setback when unshipped from Gebayl during the opening six-furlong handicap.
Gebayl had bled and lost her action, stumbling and coming down two and a half furlongs out, bringing down William Carson on Roxy Lane. Carson appeared to escape relatively unscathed.
Coumbe received treatment on track before being taken to the Queen's Medical Centre in Nottingham. He was said to be conscious when he left the track and was accompanied by the racecourse doctor, which caused about an 80-minute delay to proceedings.
"He was conscious and complaining of pelvic, leg and back pain," said clerk of the course Roderick Duncan.
Gebayl's trainer Roger Ingram revealed the filly had suffered a bad haemorrhage.
"She bled terrible. My wife spoke to Rab (Havlin) who was upsides our filly and he was going to pull up as he thought it was his horse (Doctor Hilary) that had bled. He was covered in blood. It was a bad one," he said.
The rest of the programme was completed without further incident, the last of the seven races going off only 25 minutes later than scheduled.