The Warriors hooker Thomas Leuluai needs season-ending surgery after scans confirmed he ruptured the anterior cruciate ligament in his right knee early in Saturday's NRL win over the Eels in Parramatta.
The 29-year-old veteran was helped off the field just 23 minutes into the encounter after the Warriors had also lost forward Ryan Hoffman with concussion in just the third minute.
The injuries soured the Warriors' 17-13 golden point victory, which consolidated the club in eighth place on the NRL ladder.
Leuluai is the third player in the NRL squad to have his campaign ended by an ACL injury.
He joins Ben Henry and Ngani Laumape who have both had knee reconstruction operations.
The Warriors also lost three players with ACL injuries in 2013 - Henry, Sione Lousi and Steve Rapira.
Hoffman, who wasn't able to return to the field on Saturday, is following concussions protocols.
Manu Vatuvei (sternum) and Sam Tomkins (knee) are both on target to play in the Warriors' next match against Newcastle at Mount Smart Stadium on Sunday.
Coach Andrew McFadden said he feared the worst after Leuluai's knee looked to have buckled under him as he went down untouched in the 24th minute of Saturday's golden point thriller against the Eels.
With second-rower Ryan Hoffman also hitting the showers early after a head clash in the third minute, the Warriors were forced to play the final 65 minutes of the match with 15 only men available.
A 79th minute field goal from Eels halfback Luke Kelly sent the game into extra time but a driving Bodene Thompson try was awarded in the final minute of golden point to give the Warriors their bravest win of the season.
"It was definitely memorable," Warriors skipper Simon Mannering said.
"Our backs were against the wall a bit with a couple of injuries there in key positions with Tommy and Hoffy."
"Pretty happy with that. We came up with a good play for (Thompson) to score a try."
The Warriors took advantage of Parramatta's ill-discipline in the first half to take a handy 12-0 lead into the break.
But the home side roared back into the game with two quick tries upon resumption, and levelled on Ryan Morgan's 63rd minute putdown.
Despite scoring more tries than the visitors, Luke Kelly missed all three of his conversion attempts.
Goalkicking ace Reece Robinson appeared set to take the kicking duties from Kelly for the third try but was waved away.
Eels coach Brad Arthur said Robinson was unable to kick because of a quad strain suffered in round two.
Arthur also ruled out a return next week for dumped halfback Chris Sandow who kicked eight goals from eight attempts in the NSW Cup curtain-raiser.
"He went really good but he needs to at that level," Arthur said of Sandow's performance.
"He needs to go back there and play above that level."
McFadden said Hoffman did not have a serious injury, but admitted Leuluai could be facing a long stint on the sidelines.
"I think it's the worst one. It might be ACL, but we'll have to get it confirmed. It's one of those innocuous ones and they usually turn out to be the worst case," he said.
The win consolidates the Warriors in eighth place on the NRL ladder.
They have a bye week next round.