SEATTLE – About nine minutes after the San Francisco 49ers extended their lead to 20 points against the Seattle Seahawks on Thursday night, linebacker Fred Warner was struck by an unpleasant experience of déjà vu.

Seattle had just scored 14 straight points to cut San Francisco's lead to six and got the ball back to open the fourth quarter.

For a Niners team that had blown a double-digit fourth-quarter lead in losses to the Los Angeles Rams in Week 3 and the Arizona Cardinals on Sunday, it was hard not to be in any doubt that it was an NFC West triple would be.

“(A) thousand percent,” Warner said. “It sucks, but yeah, it definitely looked familiar. I thought, 'Hey, we can go one of two ways here. We can stand firm in a hostile environment and get the game we're given.' Or we can settle for playing exactly the way we played in the last few losses.”

This time, despite another wave of injuries and an unprecedented challenge replay that went against them, the Niners persevered to grab a 36-24 win they desperately needed.

During the week, the Niners announced that Thursday's contest was the closest thing to the NFL's Week 6 must-win game. A loss would have dropped them to 2-4 overall, 0-3 in the division and 0-4 in the conference. They still had 11 games to get back into the game, but promotion would have been much more difficult.

The downside, of course, was that a win would move the Niners to 3-3, moving into a tie with Seattle at the top of the division, with an early leg against the Seahawks in a possible head-to-head tiebreaker.

“I've talked about how some tough losses are tougher than others, and when you feel like you've won those, especially division games, it makes us sick,” coach Kyle Shanahan said. “We've talked about how these two losses are a reminder of how the NFL works, and I think we've been spoiled a little bit by human nature, which is sometimes too relaxed and you can never feel too relaxed.”

The very idea of ​​a detente was difficult for the Niners to grasp given all the injuries they've dealt with this season. Without key players like running back Christian McCaffrey (Achilles tendonitis), linebacker Dre Greenlaw (torn Achilles tendon), defensive tackle Javon Hargrave (torn triceps) and safety Talanoa Hufanga (torn wrist ligament), the Niners had more health issues on Thursday night.

Cornerback Charvarius Ward completed a practice in hopes of playing despite a bruised knee, but was inactive before the game. Rookie safety Malik Mustapha, who started in place of Hufanga, caught the ball early and then left with what Shanahan called an ankle sprain. Perhaps most critically, running back Jordan Mason injured his left shoulder in the first half, came back for a carry early in the third quarter and then was available only in an emergency for the rest of the game. He finished the game with 73 yards on nine carries and caught another pass for 9 yards.

Shanahan said Mason will undergo further testing Friday to determine the severity of the injury.

“He thought he was going to be OK,” Shanahan said. “He went back in and it was just too painful for him, so he walked out… We'll find out more tomorrow.”

As if the injuries weren't enough, they also found themselves on the wrong end of a replay in which a camera angle eventually showed fans at home that Seahawks punt returner Dee Williams touched a ball that the Niners eventually hit on Seattle's 18 Shanahan said Brian Hampton, the 49ers' vice president of football administration, alerted him that Williams touched the ball, but when officials reviewed the play, they had no angle that provided clear evidence. That caused the call to fail, sparking frustration on the San Francisco sideline.

Mark Butterworth, NFL vice president of instant replay, said after the game that they didn't see the clear replay where the ball was touched until it was too late to overturn the play.

“With it being Thursday Night Football, I was sure they would have a lot of camera angles,” Shanahan said. “We threw it thinking we were going to get some better angles and then they just told me he didn’t. And then about two minutes later, I heard all the guys in the box freaking out and saying they saw a different angle, and that was a fumble.”

As it turned out, that play didn't matter as the 49ers finished the game with the help of rookies serving as backups.

Cornerback Renardo Green, playing more snaps because Ward was out, made his first career interception midway through the fourth quarter to set up quarterback Brock Purdy's winning 9-yard touchdown pass to tight end George Kittle. Rookie Isaac Guerendo, subbing in for Mason, followed suit with a 76-yard run that all but sealed the win with 1:39 left.

“We played in a lot of big games and won a lot of big games,” Kittle said. “We've lost some big games and that's just why we have experience right now… When new guys are out there and they feel the confidence of all the guys that have been there before, they feel like they fit right in and they have too this self-confidence. It just so happens that our team has been in situations like this and we've handled them pretty well, especially here on the streets in Seattle.

While the 49ers can enjoy Thursday's win for a few more days, it won't be long before they turn their attention to the next opponent on the schedule: the Kansas City Chiefs. The 49ers have never beaten Kansas City in a regular or postseason game since Shanahan took over in 2017, including, of course, two Super Bowl losses.

Kansas City is 5-0 and will be even more rested than the Niners after the bye.

Suffice it to say, no one in San Francisco will call it an unconditional victory. But there's no denying that they want it.

“It’s not like we can take revenge for the Super Bowl loss,” Williams said. “The ship has sailed…Obviously we know what kind of team this is, one of the best teams in the league, All-Star quarterback, great coach. So it will still be a difficult game. We're leaving.' Take those three days off, regroup and try to put together a complete game.