Paul Townend is facing an indefinite spell on the sidelines after dislocating his shoulder in a fall at Listowel on Wednesday.
The reigning champion jockey - who returned to action in July having suffered a foot injury at Fairyhouse's Easter meeting that saw him fitted with a special boot in riding at Punchestown - came to grief two out aboard the Jessica Harrington-trained Port Stanley.
His retained trainer Willie Mullins is hoping for a swift return to action, but Townend will seek specialist advice next week.
He said: "Paul has a dislocated shoulder. I don't know how long it is going to take and Paul doesn't know either. Sometimes you make a quick recovery, that's what we're hoping, other times it takes a bit longer.
"He is going to see a specialist early next week."
Townend was booked to ride Dysart Diamond and Sapphire Lady for Mullins at Listowel on Friday and missed a smart winner in the first-named mare.
Sean Flanagan duly stepped in to take his first ride for the Closutton handler in the Ladbrokes Handicap Hurdle, with Dysart Diamond winning by a length and quarter.
Mullins added: "I asked David Casey who was the best available, he said Sean, so I took him and it was a nice spare.
"He took the outside route when things didn't go well at the start and it seemed to suit her and she jumped beautifully for him."