Seabass has been withdrawn from the Grand National after suffering a serious injury on Monday.
Trained by Ted Walsh and ridden by his daughter, Katie, Seabass was third at Aintree in 2012 and went off the 11-2 favourite last year only to finish 13th.
The 11-year-old finished last in his warm-up race, after which he was found to have sustained ligament damage.
Pat Glynn, of owners the Gunners Syndicate, said the injury could end his career.
“He’ll be out of action for at least six months and maybe eight (months),” Glynn said.
“He suffered ligament damage mid-way through the race.
“He’s had tendon trouble before and made a full recovery. If he’s OK we might put him back into training, but we’re not sure about that at the moment.”
Tidal Bay remains the top weight of the 73 horses still engaged on April 5 after 27 came out at the latest declaration stage.
Those to have been taken out include several others owned by Graham Wylie such as last week’s controversial Cheltenham Gold Cup runner-up On His Own and the somewhat disappointing Boston Bob.
Others to have been scratched include Kauto Stone, Cantlow, Carlingford Lough, Cape Tribulation, Mon Parrain and Pandorama.
Only 40 horses can start, with four reserves.