But South Sydney coach Jason Demetriou says he and Rabbitohs teammates Latrell Mitchell and Cam Murray are "every chance" to shake their injuries off by June 21 - when the Blues hope to level the series at Suncorp Stadium.
Veteran five-eighth Walker tweaked his quad warming up for Rabbitohs training on Friday morning and left the field, replaced in the side to face St George Illawarra this weekend by tyro Dean Hawkins.
A hamstring injury to Nathan Cleary has forced Blues coach Brad Fittler to rethink his halves combinations for Game II and Walker had been considered a serious chance to earn a call-up.
Just as Fittler has favoured the Penrith halves combination of Cleary and Jarome Luai, Walker's chemistry with former South Sydney teammate Adam Reynolds could spark a Blues attack that faltered in the series opener.
Walker has four games of Origin experience and played all three matches of the 2020 post-season series.
But it remains to be seen whether Fittler would be willing to bide his time with Walker if the injury stretches beyond the weekend and into next week's camp.
Walker's South Sydney teammate Campbell Graham was dismissed from camp for Game I after a long-term sternum injury affected his ability participate in the side's early training sessions.
"It's an injury that's really short-term,"Â Demetriou said of Walker's quad niggle.
"It's only happened a couple of days before the game so we're not in a position to risk him but Origin's not for nearly two weeks.
"He is every chance of being available.
"For us, we know he'll be back for the game after the bye (in round 16), which is only a few days after Origin."
Demetriou said the Rabbitohs' onerous fixture had likely contributed to Walker's injury; Souths are one of only three sides yet to have a bye through 14 rounds.
"The boys are creaking a little bit," Demetriou said.
Souths fullback Mitchell missed the series opener with a calf injury and will also sit out of the Rabbitohs' clash with the Dragons on Saturday.
Souths captain and Blues forward Murray misses with the groin injury he suffered against Gold Coast last week.
Both Mitchell and Murray will know before NSW teams are named on Tuesday morning whether they are fit enough to line up in Game II.
"(Mitchell) is in a good place, physios are working overtime with him as well to give him every chance to be available," Demetriou said.
"If he's able to run, he'll be ready to go. I'd love to see him out there.
"It's one of those injuries where every couple of days makes a big difference, when you've got a low-grade. We'll see how he responds. Cam Murray is the same."
Souths hooker Damien Cook is likely to earn a Blues recall after incumbent hooker Api Koroisau broke his jaw making a tackle during Wests Tigers' loss to Gold Coast on Thursday.
"(Cook) realises how blessed he was to have that time with NSW and if that opportunity comes again, he'll take it with both hands," Demetriou said.
