The Roosters' premiership hopes were dealt the harshest possible setback on Sunday, with Walker suffering a ruptured ACL in his team's loss to Canberra.
There are also fears Smith has also suffered ACL damage after an Elliott Whitehead hip-drop tackle, with the Roosters hooker set to undergo another scan and see a doctor on Monday.
The Sydney Roosters are sweating on an injury update on Brandon Smith. (Mark Evans/AAP PHOTOS)
The pair's injuries came on a horror afternoon for the Tri-colours, who also lost Victor Radley to a shoulder injury and Nat Butcher to concussion.
Butcher should at least return for the finals, but Radley is no guarantee as he also awaits the results of scans.
In the short term, the Roosters' injuries threaten to stop the club's charge towards their first premiership since 2019.
No club has won the grand final without their first-choice halfback available during the NRL era, with Sandon Smith likely to be the man to fill the No.7 jersey.
Smith's absence will also likely mean Connor Watson reverts back to the hooker role, after starting there three times this season.
Connor Watson shapes as the likely replacement at hooker for Brandon Smith. (Mark Evans/AAP PHOTOS)
"We've got a squad for that reason," coach Trent Robinson said.Â
"You guys don't get to see them always, but you've got to believe in who's coming next.
"So let's go, let's get excited about moving on to next week."
In the long term, the implications could be even more significant for the Roosters.
The club will lose more than 750 games in experience at season's end, with Luke Keary, Jared Waerea-Hargreaves, Joey Manu and Joseph-Aukuso Suaalii all exiting.
Walker's injury will mean they will have a brand new halves combination for at least the first half of 2024, with ACL ruptures generally requiring a nine-month recovery.
Sandon Smith will therefore likely partner Chad Townsend in the halves, as the Tri-colours face their biggest test in the halves since 2016.
Watson may be forced into a long-term hooker switch to start next year, if Brandon Smith does face a lengthy rehabilitation.
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