O'Faolains Boy is out of the Crabbie's Grand National after trainer Rebecca Curtis found the nine-year-old to be lame on Saturday morning.
It is a blow to the Welsh trainer as she felt O'Faolains Boy, winner of the RSA Chase in 2014, was in tremendous shape for a crack at the Aintree spectacular.
He had shown he was coming back to his best when seventh in the Timico Cheltenham Gold Cup last month. A best-priced 33-1 for Aintree glory, he was to be ridden by Brian Hughes.
"He was absolutely fine yesterday but when he pulled out this morning he was just a bit sore," Curtis said.
"He has a slight bit of swelling under his hock.
"He'll be fine in a few days but obviously it rules him out for today, unfortunately. Why today?"
Curtis expects to get O'Faolains Boy back on the track before the end of the month.
"He'll be absolutely fine again next week," she said.
"He's in the Scottish National and the bet365 Gold Cup (at Sandown) and there's also Punchestown so he will go again this season.
Curtis still has the The Romford Pele is the big race, due off at 5.15pm.