SEATTLE – The San Francisco 49ers held on and defeated the Seahawks 36-24.

Heading into Thursday night, the 49ers weren’t calling it a must-win game.

At least mathematically, there’s no such thing in Week 6 of the NFL season. But defensive end Nick Bosa and his teammates were clear Tuesday in their assessment that this was the closest given the circumstances.

At 2-3 overall and 0-2 in the NFC West division, a loss to the Seahawks wouldn’t have buried the 49ers’ season, but it would have dug the hole deep.

Even as things piled up Thursday night in Seattle against San Francisco — more injuries, unprecedented replay angles and special teams issues, to name a few — the 49ers sent a reminder that they won’t let their Super Bowl window closes without a fight.

Somehow, even at 3-3, these Niners are back at the top of the division, tied with Seattle, but now hold the head-to-head tiebreaker.

That happened despite playing without cornerback Charvarius Ward and losing running back Jordan Mason (left shoulder) and safety Malik Mustapha (ankle) to injuries that kept them out for large portions of the game while seeing others like tight end George Kittle and receiver Deebo Samuel Sr. stumbles at various points of the field.

Additionally, the 49ers overcame a bizarre incident in which coach Kyle Shanahan disputed that Seahawks returner Dee Williams touched a punt and San Francisco recovered it deep in Seattle territory. Officials confirmed the call that Williams did not touch it, although “enhanced” replays were shown to viewers suggesting he did. That replay was not available to officials in Seattle, according to the broadcast.

The 49ers probably should have locked up Seattle much sooner. But they have made it clear in the first six weeks that nothing will come easy this year. As of Thursday night, the Niners have proven that they are up for the challenge when things don’t go their way.

QB breakdown: Brock Purdy was under pressure for much of Thursday’s match, but that didn’t stop him from finding ways to make the plays needed to get the win. Purdy finished 18 of 28 for 255 yards with three touchdowns and no interceptions. It was exactly what the 49ers needed.

Troubling trend: At some point, the 49ers will have to address their special teams woes. It was an issue in the biggest moments of their Super Bowl LVIII loss to the Kansas City Chiefs and persisted through the first six games of this season.

On Thursday night, the Niners looked ready to put the Seahawks away with a touchdown drive to open the second half. But they gave those points back almost immediately, allowing a 97-yard kick return for a touchdown.

That’s in addition to the fake punt they allowed for a first down that turned the Week 3 game against the Los Angeles Rams into a loss, the 39-yard kick return they allowed that led to kicker Jake Moody getting hurt in last week’s loss to the Cardinals and a handful of other costly mistakes this season.

It’s hard to make big changes on special teams in the middle of the season, but something has to be done. Soon.

Silver lining: Injuries to Mason and Ward led the 49ers to turn to a pair of rookies to fill the void. There were some tough moments, but cornerback Renardo Green and running back Isaac Guerendo were up to the task and made a few plays that helped tie the game together.

Green intercepted Seahawks quarterback Geno Smith in the fourth quarter to help the Niners extend the lead to double digits, and Guerendo finished with 10 carries for 99 yards, including a 76-yard burst that ended any hope Seattle had on a comeback. –Nick Wagoner

Next game: vs Chiefs (4:25 PM ET, Sunday, October 20)

The Seahawks are still trying to get over the hump that has been the 49ers, who have made their numbers in spades over the last two-plus seasons.

For now, they’ll have to settle for progress against their division rival, whatever comfort that brings to a Seahawks team that has lost three straight games after starting 3-0.

The gap between Seattle and San Francisco didn’t look as wide Thursday night as it did when the 49ers won the previous five meetings by a combined score of 148-72. This would be another blowout before the Seahawks stormed back in the third quarter to make it a game. It was a valiant effort for a team short-handed and exhausted after playing three games in 11 days.

But if they can’t beat the 49ers at home with San Francisco’s defense struggling and Christian McCaffrey missing on offense, when can they?

QB breakdown: The 49ers defense has made things difficult for Smith, and it was more of the same on Thursday night. This time it wasn’t because he was overwhelmed by pressure from San Francisco, as he had been in previous meetings. But he couldn’t do much with the clean pockets he got: He threw for 312 yards, one touchdown, two interceptions and an un-Smith-like completion rate of 57.7%.

His first interception came on a throw to Tyler Lockett, while the second went right to cornerback Green, who had jumped a pass to DK Metcalf. Smith had some bad luck earlier this season, with two of his interceptions coming on tipped throws. But there was nothing bland about this one.

Troubling trend: The Seahawks turn the ball over far more than they take it away. Only four teams had a worse turnover margin than theirs entering Thursday. That’s now minus-6 after Smith’s two interceptions and Laviska Shenault Jr.’s lost fumble. during a kick-off return. Shenault made up for the mistake by returning a later kickoff 97 yards for a touchdown, but this is not a sustainable trend.

Biggest hole in the game plan: The Seahawks’ run game remains an issue. Through the first five games, the problem was largely that they relied far too heavily on their passing game, which ranked them last in the NFL in designed rushing. They ran it harder Thursday night but didn’t have much success, totaling just 52 yards in 20 attempts before the two-score deficit forced them into throwing mode. Kenneth Walker III scored a touchdown, but gained only 32 yards on 14 carries. –Brady Henderson

Next game: at Falcons (1 p.m. ET, Sunday, October 20)