The JP McManus-owned Double Seven, who was among the favourites to win this year's Grand National, has been ruled out until 2016.
The nine-year-old finished third under Tony McCoy during the showpiece Aintree race last year, as well as winning five other races in a row.
However, trainer Martin Brassil has confirmed that an injury will prevent the bay gelding from going two better this time around.
"He's out for the season, unfortunately. We're very hopeful that we'll be able to get him back in [training] next season and go back to Aintree again, though," said Brassil.
"He's young enough to go back and he's on a rating now where Aintree has to be on your mind, especially as he ran so well last year. It's a shame he won't be there this year but, with a bit of luck, he'll be back there again."
Shutthefrontdoor is now the outright favourite to win the National, which will take place in April.
