Brian Harding is set for a spell on the sidelines after a fall at Musselburgh on Tuesday.
Harding took a tumble from Shotofwine in the three-mile handicap hurdle.
Initially it was reported that the weighing room's elder statesman was not badly injured, but on further inspection problems were found.
His boss Nicky Richards said: "Brian's not in a good way, unfortunately, it's worse than first thought.
"He's got damage to his T7 vertebrae and the horse kicked him at the bottom of his back and bruised a kidney.
"He'll be off a while longer than first thought."