Prince De Beauchene has been ruled out of the John Smith's Grand National at Aintree on Saturday week.
The 10-year-old is suffering from a stress fracture in his ilium and will miss the race for the second year running after a hip problem also saw him sidelined in 2012.
Willie Mullins' charge had been among the leading contenders for the Aintree showpiece after winning over hurdles on his return and finishing second in the Bobbyjo Chase last time.
"We have had some bad news about Prince De Beauchene," the trainer told www.wpmullins.com.
"He had not been striding out for the last few days and following a bone scan at Troytown Veterinary Hospital, it has been confirmed he has a minor stress fracture in his ilium.
"He will require at least six weeks box rest, so unfortunately he will the Aintree Grand National."
Mullins and Prince De Beauchene's owner Graham Wylie still have ante-post favourite On His Own in the National field.