SEATTLE -- As the guttural screams of the San Francisco 49ers coaching staff echoed through the press box and general manager John Lynch rushed on the field and scooped up the game ball with Niners players celebrating wildly around him, coach Kyle Shanahan stood stoic, holding his breath and waiting for a final verdict.

San Francisco rookie linebacker Dre Greenlaw had just tackled Seattle Seahawks tight end Jacob Hollister an inch or two short of the goal line on fourth down, apparently cementing the biggest 49ers win since the 2013 NFC Championship Game.

Not far from Shanahan's mind was what took place on Dec. 15, when a similar play initially went San Francisco's way before a review overturned the call on the field and gave the Atlanta Falcons the winning points for an upset.

"I wasn't ready to celebrate anything," Shanahan said. "[The Atlanta game] kind of ruined my celebration, to tell you the truth. I wanted to wait until I saw it on the scoreboard."

Sure enough, the scoreboard revealed what Shanahan had hoped and a lengthy review confirmed it for the officials: Hollister was short, Greenlaw had made the most important tackle in recent 49ers memory, and the Niners had escaped with a 26-21 victory in the place that had been their own, personal house of horrors for most of the past decade.

"I just made sure that I kept my feet on the goal line ... and just made a tackle that my coaches and teammates will be proud of," Greenlaw said. "I'm just thankful to be able to make the play."

With Greenlaw's tackle came a bevy of riches: the NFC West division crown, a first-round bye, the No. 1 seed and home-field advantage throughout the NFC playoffs. All of that just 248 days after using the No. 2 pick in the NFL draft, a selection gained through a brutal 4-12 season in 2018.

Sunday night's game was the 49ers' fifth straight in which the outcome was determined in the closing seconds. The Niners lost to Baltimore and Atlanta but beat New Orleans and the Rams.

"We worked for this all year," Shanahan said. "That's always the goal going in, just to get in the tournament. To get in there with the No. 1 seed feels very good. We were going to be ready to deal with whatever we had to tomorrow, whether if we had to go play three games, but I know we're much happier that we can stay at home now when you're two games away from the big one. We're going to enjoy this bye week, but very proud of the guys.

"We've had to win a lot of different ways this year. I keep feeling like we've done it every way possible and then we find a way to do it."

It was the Niners' first win in Seattle since Dec. 24, 2011, and moved them to 13-3 on the season, their best record since 2011. That nine-win improvement makes them the eighth team in league history to improve their win total by at least nine games from the previous season, according to the Elias Sports Bureau.

The division crown is San Francisco's 20th, the top seed in the NFC is their first since 1997, and their 7-1 road record is their best mark since 1992. This is the fifth time the 49ers have earned the No. 1 seed, advancing to the NFC championship in three of the previous four instances and winning the Super Bowl the other.

With the loss, Seattle dropped to 11-5 and claimed the No. 5 seed in the NFC playoffs. The Seahawks will visit the Philadelphia Eagles next Sunday in a 4:40 p.m. ET wild-card game.

The 49ers will host their first playoff game at Levi's Stadium since it opened in 2014 on Jan. 11 or Jan. 12 in a divisional-round matchup.

"It's a great feeling just to get the 1 seed, to be NFC West champs," cornerback Richard Sherman said. "That's your goal coming into the year. That's the first thing that you have got to accomplish so that you get a home game in the playoffs ... Our team believed In each other. That's what makes it special."

As the clock ticked down Sunday night, it appeared Seahawks quarterback Russell Wilson was again going to conjure enough magic to give Seattle its own special moment. That came after the Niners controlled the game from kickoff.

San Francisco held Seattle scoreless in the opening half, the first time since Week 15 of 2017 that's happened and only the third time Seattle has been shut out at the half of a home game since Wilson became the starter.

When the Seahawks' offense finally got rolling in the second half, Niners quarterback Jimmy Garoppolo & Co. repeatedly mustered strong responses. After Seattle's first two touchdowns in the second half, the Niners responded with a touchdown of their own.

Garoppolo finished 18-of-22 for 285 yards with no touchdowns and no interceptions for a passer rating of 118.8. Rookie receiver Deebo Samuel did a lot of that damage, posting five catches for 102 yards with a 30-yard rushing touchdown.

"This whole season has been complementary football between our offense, defense and special teams, and tonight was no different," Garoppolo said. "They'd step up and make a huge play, we'd step up and make a huge play. It was just everyone stepping up when their number was called."

Now, the Niners can look ahead to a much-needed bye week, something they haven't had since Week 4. It offers a chance to get defensive end Dee Ford (quadriceps and hamstring), safety Jaquiski Tartt (ribs) and guard Mike Person (neck) back closer to full strength and on the field. It also creaks the door open just a bit more for a potential return by linebacker Kwon Alexander from a torn left pectoral.

When they return from that time off, the Niners could find themselves in a rubber match with the Seahawks in Santa Clara. Seattle beat San Francisco there on Nov. 11 in a tense, overtime thriller.

If New Orleans beats Minnesota in the wild-card round and the Seahawks advance past the Eagles, Seattle and the 49ers would meet again. Given how the first two meetings went, that would surely provide plenty of drama and help reignite what not long ago was football's fiercest rivalry.

For now, the Niners, wearing their "The West is Not Enough" T-shirts and division champion hats, were content to celebrate a win that not only put them in prime playoff position but, at least temporarily, erased a lot of bad memories.

"Honestly, it's been a hard place to play here," left tackle Joe Staley said. "Everybody knows about our record here since 2011. I've been a part of all those games and it feels good to win this one."