The jockey, pictured, was due to partner the Willie Mullins-trained Sir Des Champs in the big race and in his absence leading female amateur Nina Carberry will come in for the ride.
Walsh, who has won the National twice, endured an afternoon to forget on Merseyside, first coming to grief when riding 1-5 favourite Vautour in the JLT Melling Chase.
After suffering another fall from Blood Cotil when tackling the Grand National fences in the Crabbie’s Topham Chase, Walsh did not take up his mounts on Bellshill in Doom Bar Sefton Novices’ Hurdle or Battleford in the concluding bumper.
Trainer Willie Mullins, though, initially said he expected him to return to action on National day. However, it later emerged he had suffered a hairline fracture to his wrist and Walsh will now have to watch on from the sidelines.
His sister and agent Jennifer Walsh said: “He has a small fracture of his wrist and a lot of bruising, so he won’t be riding on Saturday.
“It happened after the fall from Blood Cotil. He will see his own surgeon when he gets home on Monday.
“It’s disappointing, but he’s walking and talking and any day you can do that is a good day.”
Mullins said: “It’s been one of those days – they say it’s character building.”
Walsh will also miss high-profile rides on Yorkhill in the EZ Trader Mersey Novices’ Hurdle and the brilliant Douvan in the Doom Bar Maghull Novices’ Chase.
Ireland’s champion trainer has been quick to make alternative riding plans. “Nina Carberry will ride Sir Des Champs and Paul Townend will ride Yorkhill and Douvan,” he added.