Robbie McNamara is reported to "very stable" after undergoing spinal surgery at the Mater Hospital in Dublin on Saturday.
The jockey was due to partner last year's Cheltenham Gold Cup winner Lord Windermere in the Crabbie's Grand National at Aintree, but suffered multiple injuries after coming to grief in a fall at Wexford.
He was initially taken to Wexford General Hospital, before being transferred on Friday night.
Dr Adrian McGoldrick, chief medical advisor for the Irish Turf Club, said: "Robbie has multiple fractures, abdominal bleeding and a collapsed lung.
"He had spinal surgery this morning and is in the high dependency unit at Mater (Hospital), but he is very stable.
"We will hopefully have more news on Sunday. He is certainly in a lot better place than he was last night."