SANTA CLARA, Calif. (AP) — Any questions about the San Francisco 49ers' offensive line after getting overwhelmed in two late-season losses to Seattle last season have been quieted with an impressive start this season.

The Niners once again protected Brock Purdy well on Sunday even against Denver's fierce defensive line, becoming the first team in 21 years to open the season with four straight games without allowing a sack after beating the Broncos 24-14.

“I think everybody in the locker room goes through those times where you’ve got to be a little bit, I guess, for lack of a better word, crazy, in a sense to where you’ve got to believe that you’re the best,” left tackle Trent Williams said. “It’s the belief and the confidence that allows you to play like you can be that. I’ve always thought we had the talent to be one of the best O-lines in the league.”

The 49ers (4-0) are playing like that early this season with returning starters Williams, Jake Brendel, Dominick Puni and Colton McKivitz and newcomer Connor Colby doing their best to keep Purdy clean.

San Francisco is the first team since Indianapolis in 2005 to open the season without allowing a sack in the first four games and just the fifth team to do it since team sacks began being tracked in 1963.

The latest clean sheet came against a Broncos defense that has led the NFL in sacks since the start of the 2024 season.

“That says a lot, especially versus that front," coach Kyle Shanahan said. "They’re a really good pass rush team. Says a lot that we were able to run the ball so much too, so we could stay balanced and not let them be one-dimensional. I thought Brock did a good job avoiding some too. It starts with the O-Line, but collectively it’s been a huge deal and definitely wasn’t expecting to do that all the way up until now.”

Purdy has been under pressure on 35 drop-backs, according to Pro Football Focus, the second fewest for any team so far this season. But he has also done a good job getting rid of the ball quickly, as well as escaping pressure when it comes.

“For me to be able to drop back behind those guys, I’m extremely blessed,” he said. "Obviously it’s a long year. We’ve got a long ways to go as an offense and as a team, but just extremely happy with how they’re playing and what they’re playing for.”

The next test comes Sunday at Seattle against a Seahawks team that sacked Purdy five times and held the 49ers out of the end zone in wins in Week 18 last season to clinch the division and in the divisional round.

Passing to George Kittle. Kittle had four catches for 70 yards and a game-sealing 56-yard touchdown in his fourth game back from major surgery on his Achilles tendon. Kittle looks back in his usual form and currently leads all tight ends with four TD catches and ranks third with 244 yards receiving. Purdy has a 139.6 passer rating in his career when targeting Kittle, the best mark for any QB-pass catcher combination since at least 2000.

Third down defense. The Niners allowed Denver to convert on 8 of 17 third downs and rank fifth worst in the league over the past three weeks by allowing conversions on 48% of third downs.

Siran Neal. A week after a punt hit his leg while he was blocking to lead to a turnover, Neal made the momentum-changing play when he stripped Marvin Mims Jr. on a punt return to set up the Niners' offense with a short field for the go-ahead touchdown.

Secondary receivers. The injuries that have sidelined Ricky Pearsall, De'Zhaun Stribling and Demarcus Robinson have left San Francisco thin at receiver. Brandin Cooks, Jacob Cowing and Jordan Watkins ran 22 combined routes and were targeted just twice with no catches.

FB Kyle Juszczyk will miss a few weeks with a hyperextended knee and bone bruise. ... S Marques Sigle (high ankle sprain) also will miss a few weeks. ... CB Upton Stout (shoulder) is day to day and could play this week. ... DE Nick Bosa (calf) and DT James Thompson (ankle) will remain sidelined this week. ... DE Mykel Williams (knee) will ramp up practice this week and could be activated from the physically unable to perform list.

15. The 49ers have scored 16 touchdowns this season with 15 of them coming from players in their 30s. That is tied with the 2002 Raiders for the most TDs by players 30 or older in the first four games of a season.

The 49ers visit Seattle on Sunday in search of their fifth 5-0 start in the Super Bowl era. San Francisco made the Super Bowl in three of the four previous seasons, including in 2019 and '23 under Shanahan.

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