Brian O'Connell faces up to two months out of action after an operation on his shoulder
O'Connell, who has ridden the likes of Last Instalment and Don Cossack to Grade One wins, suffered the damage at Tramore on October 5.
He returned a week later but felt some discomfort and an MRI scan showed he needed surgery.
"I'm going to be out for a couple of months," O'Connell told Press Association Sport.
"I took a fall in Tramore two weeks ago and I was off for a week. I came back and rode for three or four days while I was waiting on the results of a MRI scan.
"The results showed that I had torn ligaments and tendons in my shoulder.
"I met with a specialist on Tuesday and he operated on me on Wednesday morning.
"I'll be on the sidelines for a couple of months anyway and it's too early to think of a date for coming back.
"There is never a good time of year to get injured but this is always an exciting time getting into the real National Hunt season.
"It's a pity but that's the joys of the game."