SANTA CLARA, Calif.—The Seahawks defense needed one more stop to give Geno Smith and the offense a chance at a game-winning drive. One more stop to prevent the 49ers from closing out a victory that would have been a big blow to for a team that had lost five of six heading into the bye.

And as it had done so many times throughout Sunday's game at Levi's Stadium, Seattle's defense made the plays it needed to make, forcing the 49ers to punt from just past midfield, setting up Smith and the offense for the late-game heroics that led to a 20-17 Seahawks victory.

"We played complementary football," said cornerback Devon Witherspoon, who had eight tackles and three passes defensed, the first of which was intercepted by Johnathan Hankins. "We never gave up, even when things started to take a turn, and we always had each other's backs out there. So I think being together, staying together as a football team, knowing it's only us, it's us against them, that got us through this."

Witherspoon was involved in the final key play for Seattle's defense, blitzing on third-and-long to force Purdy to check the ball down rather than potentially throw down field for a first down, allowing Coby Bryant to make a stop to set up a punt.

"We're doing the things that we do best," Witherspoon said. "We make other teams have to play off of us, so that's what it really is. Mike (Macdonald), he's been in his bag lately, and we're just bringing it to light."

Sunday's performance wasn't a perfect one for Seattle's defense, which allowed two long touchdown drives, too much scramble yardage to Brock Purdy, and a 7 of 11 conversion rate on third down, but overall it was a second straight strong performance for Seattle's defense, and one that showed just how far that unit has come in recent weeks. The last time Seattle and San Francisco faced off in Week 6, they gained a season-high 483 yards on their way to 36 points. In this outing, the 49ers gained just 277 yards and were not able to make the explosive plays that were so crucial in the previous outing. In that Week 6 game, the 49ers had five plays of 20 or more yards, including two separate gains of 76 yards. On Sunday, their longest play was 22 yards, and that was their only gain of 20 or more yards.

"As a defense, it was a winning performance, with room to grow, which is exciting," Macdonald said. "It's good football, it's some of our best football, but it's not our absolute best."

This performance followed a strong showing against the Rams in which L.A. had seven three-and-outs and averaged just 2.8 yards per rush, and showed the continued growth of a defense that was quite a bit different than the unit that took the field against the 49ers last month, both because the Seahawks had several players back from injury, including cornerback Riq Woolen and defensive tackle Byron Murphy II, and also because of some changes made by the coaching staff and front office, most notably with linebacker Ernest Jones IV arriving in a trade last month, and with rookie linebacker Tyrice Knight replacing Tyrel Dodson this week.

"This defense, I look to my left, I see T-Knight, I look behind me and I see Spoon, I see those safeties, and I look in front and I see those dogs, man, we can go out there and play with anybody," said Jones, who had a team-high 13 tackles, giving him 37 in three games with Seattle. "We come out there and show what we are and play physically, be disciplined in the moments that we need to be, which really, at all moments, I think we can be something special."

For the Seahawks, who started the year 3-0 before hitting a rough patch, Sunday's win felt a lot like the early-season ones for the defense, which wasn't flawless in its performance, but was plenty good enough to get a win. The biggest difference, of course, is that they got it done against the 49ers, a team that has given Seattle's defense so much trouble in recent years.

"It feels like it did at the beginning of the season," Macdonald said. "We had a winning performance, good enough to win the football game. There's things we're going to be chasing as well like third-down effectiveness, how well we're rushing the quarterback with four. Some of the communication as the drive starts to extend. Those are things we have to be really good at to take the next step as a defense. That's going to be our challenge. The communication, the preparation, all that stuff we're chasing on the front end Monday through Saturday into Sunday morning. I've gotten really good feedback from some of our leaders. That's encouraging when you feel you're on the right path and getting these guys ready to go. We'll keep doing that."