Super Bowl champion Seahawks defense vs. Brock Purdy's 49ers will be one of Week 5's top battles. Here's why

Purdy is playing the best of any QB in the league this season, but now he'll face the NFL's No. 1 defense

Oct 9, 2026 at 7:28 am ET • 4 min read

How well is San Francisco 49ers quarterback Brock Purdy playing right now in his team's 4-0 start to the 2026 season? 

He's on such a tear that he created his own statistical club. Purdy is the only quarterback in NFL history to start 4-0 with one or fewer sacks, fumbles or interceptions combined, according to CBS Sports Research. Purdy leads the NFL in passer rating (126.2), passing success rate (61.9%) and expected points added (EPA) per dropback (0.53) while co-leading the league in passing touchdowns (11). Purdy's EPA per dropback of 0.53 is the second-highest through four games in the 21st century, behind only Tom Brady's 0.59 EPA per dropback in New England's 16-0 2007 regular season. He's also been accurate, ranking fifth in the NFL in completion percentage (69.9%).  

However, he'll now be tested by the best of the best in Week 5 when playing at Lumen Field against the defending Super Bowl champion Seattle Seahawks. San Francisco leads the NFL in yards per play this season (6.8), but Seattle leads the NFL in yards per play allowed (4.0).

In each of the last two showdowns, the Seahawks' defense had the edge over the 49ers' offense. In Week 18 of the 2025 season, with the NFC West title and the conference's No. 1 seed on the line, Seahawks head coach Mike Macdonald and his "Dark Side" defense threw 49ers head coach Kyle Shanahan, Purdy, and their offense in a body bag in a 13-3 win. That marked San Francisco's fewest points scored in a game since Week 1 of the 2017 season, Shanahan's first game as the 49ers' head coach. 

The last meeting occurred in January in the NFC divisional round at Lumen Field. Seattle dropped the hammer on San Francisco in a 41-6 victory that began with Rashid Shaheed taking the opening kickoff back for a touchdown. That 35-point margin of victory tied the record for the most lopsided Seahawks playoff win in team history. 

Sunday is another battle — likely one of the best of the weekend. 

Will Purdy finally find success against Macdonald's Seahawks defense?

Seattle's current "Dark Side" defense under Macdonald is on pace to have a profile similar to their "Legion of Boom" predecessors from the 2010's if they remain on this pace. The Seahawks defense has surrendered the fifth-fewest points per game (18.3), the fewest total yards per game (246.8), the fewest yards per play (4.0) and the fewest passing yards per game (144.8) while tied for the most interceptions (6) in 2026. At the moment, they are on pace to become the first team since the 2013-2014 Seahawks to lead the NFL in total defense in consecutive seasons.

So, where will the matchup of Purdy and Co. vs. the "Dark Side" Seahawks be won? When Purdy drops back to pass on early downs. He leads the NFL in EPA per dropback (0.50) when passing on early downs, while being tied for the most touchdown passes in the NFL (7) on early downs. 

A big factor in that success is that Purdy typically doesn't face pressure on those early down drop-backs, as he has an NFL-low 24.7% pressure rate in those situations, per TruMedia. He also averages 2.88 seconds before pressure comes on early down dropbacks, the fourth-longest average in the league, per the NFL's Next Gen Stats. When he has a clean pocket on early downs, Purdy is averaging 9.6 yards per attempt, the third-most in the league per Next Gen Stats. 

Purdy's early down success will be thoroughly tested by the Seattle defense. The Seahawks have created the second-highest pressure rate (44.2%) on early downs even though they blitz at the second-lowest rate (17.9%) in those situations, per TruMedia. The only defense in the league with a higher early down pressure rate is the Vikings (48%), who have blitzed 60.5% more often (78.4%). That means Seattle is winning with their front four at an incredibly high rate on early downs. 

Seahawks edge rusher Uchenna Nwosu (22.2% early down pressure rate), edge rusher DeMarcus Lawrence (15.5% early down pressure rate) and defensive tackle Leonard Williams (14.8% early down pressure rate) all rank inside the top 25 in early down pressure rate individually entering Week 5, per TruMedia. 

49ers offensive line will need to step up

That means a lot will be asked of 38-year-old, 12-time Pro Bowl 49ers left tackle Trent Williams and the rest of Purdy's offensive line. The Seahawks have been able to fluster the three-time first-team All-Pro left tackle at a slightly higher rate than normal since Macdonald became Seattle's head coach in 2024. Williams has allowed 12 pressures without a sack on 143 pass-blocking snaps in four combined matchups with the Seahawks' defense since, including the playoffs, for an 8.4% pressure rate, compared to an 8.1% rate allowed against all other opponents over the last three seasons, per the NFL's Next Gen Stats.

However, half of the 12 pressures Williams allowed in this span happened during his 35 matchups with edge rusher Boye Mafe  (17.1% pressure rate), who joined the Cincinnati Bengals in free agency this past offseason. Lawrence, with two, is the only other Seahawks defender to have multiple pressures when matched up with Williams in the Macdonald era (since 2024).

Brock Purdy career vs. Mike Macdonald's Seahawks, Since 2024 including playoffs	Stats
W-L	2-3
Team PPG	15.8
Pass yards per attempt	6.6
TD-INT	6-5
Passer rating	85.9
Times sacked	8

Simply staying ahead of the chains on a down-to-down basis and not having negative plays is an antidote against any intimidating defense. That is something Purdy and the 49ers' offense as a whole have specialized in through the first quarter of the 2026 season. 

As an offense, San Francisco possesses the lowest rate of plays losing yards (2.2%) by any team through the first four games of a season in the 21st century (excluding kneel downs), per CBS Sports Research. Purdy himself has produced the lowest negative play rate (0.8%) by any quarterback through four games this century as well.

The battle of wits of Shanahan and Purdy versus Macdonald and his "Dark Side" is shaping up to be THE head-to-head battle of the entire Week 5 slate.