His likely replacement, Parramatta's Reed Mahoney, has also been sidelined by injury and is unavailable for the second State of Origin game.
At the same time, AJ Brimson — who played as their bench utility in game one — missed Sunday's game for the Gold Coast Titans with severe bone bruising on his knee and was later ruled out of Origin selection.
That means St George Illawarra Dragons veterans Andrew McCullough and Ben Hunt also come into the squad while Cowboys prop Francis Molo will make his Origin debut from the bench.
Fellow Warrior Roger Tuivasa-Sheck told the Herald on Saturday that placing Walsh into the red-hot cauldron that is Origin was a gamble, like Green, he would also take.
"I'm that big of a fan I say throw it at him and see what he has got. I'm just a fan of him and if he handles, he handles it; if not, he will take it as lessons."
However, while Tuivasa-Sheck said Walsh was capable of delivering on the park, he said the off-field noise could be problematic.
"[If] he gets in there, he'll play the game like it's a game," said Tuivasa-Sheck. "But probably all the pressure and the hype beforehand is what is too much for him."
Meanwhile, Walsh himself told the Herald he was keen to rise to the challenge.
"I haven't had too many first-grade games. But that doesn't mean that the confidence isn't there - that I could go out and have a crack."
In front of the biggest crowd at Townsville's new Queensland Country Bank Stadium, that was largely Maroons dominated, NSW turned in its biggest ever victory, 50-6, in Origin history in game one.