Injury has forced Silver Birch out of next month's Grand National and the remainder of the National Hunt season.
Silver Birch won the Becher Handicap Chase at Aintree in November
The Welsh National winner had been vying with Amberleigh House and Clan Royal for Aintree favouritism and was as low as 12-1 with some firms.
But trainer Paul Nicholls said he will not risk the eight-year-old after detecting a problem with his leg.
"We noticed on Thursday night that his leg was not quite right and sadly he has heat in it, which has ended his campaign," Nicholls said.
"We will scan him on Monday to confirm the extent, but unfortunately he won't run again this season."
A total of 130 horses were provisionally entered in the 9 April race, including 30 from Ireland and four from France.
The first three home in 2004 - Amberleigh House, Clan Royal and Lord Atterbury - are still among the entries.
Bindaree, winner in 2002, and the 2003 winner Monty's Pass are also still on course for Aintree.
For saftey reasons, there will be a maximum 40 runners on the day.