Can Brock Purdy and Kyle Shanahan Crack Mike Macdonald’s Defensive Code?

Sunday’s contest in Seattle represents a pivotal moment for the 49ers in Week 5. With first place in the NFC West hanging in the balance, a victory would give San Francisco a significant advantage in what has become one of the league’s most competitive divisional races.

While 49ers-Seahawks matchups are inherently intense, San Francisco enters this game with added motivation following last season’s disappointing conclusion. The Seahawks’ defense stifled the 49ers twice in three weeks, most memorably with a 41-6 defeat in the NFC Divisional Round.

This challenge carries particular weight for 49ers quarterback Brock Purdy and head coach Kyle Shanahan, who have consistently dismantled opposing defenses but have found themselves repeatedly stymied by Seahawks defensive coordinator Mike Macdonald.

Their struggles against Macdonald date back to his tenure with Baltimore, where Purdy threw four interceptions in a 33-19 loss on Christmas night that derailed his MVP campaign in 2023. Though the pair secured a measure of revenge with a 36-24 victory in 2024, San Francisco has failed to exceed 17 points in any of their last four encounters. Worse yet, they have yet to score a touchdown in their past two meetings.

Macdonald has emerged as Shanahan and Purdy’s kryptonite over recent seasons. Now that he’s coaching a division rival, there’s no escaping his defensive prowess.

To assert dominance over the NFC West—and potentially the entire conference—Shanahan must demonstrate his standing among the NFL’s elite offensive minds, while Purdy seeks to cement his case in this year’s MVP conversation. Both objectives hinge on overcoming Macdonald’s defensive scheme first.

But is that even possible? To answer that question, we need to examine why Macdonald’s defense has proven so insurmountable for Shanahan and Purdy.

Let’s start with Shanahan’s own assessment:

“[It’s] how sound they are, yet [they’re] still aggressive,” Shanahan observed this week. “When they’re aggressive, they’re rarely irresponsible. It’s tough to get big plays on them. I think they’ve been no. 1 in the league two years in a row in that, whether it’s run or pass game.”

Shanahan’s analysis holds weight. No defense has been more effective at preventing explosive plays over the past two seasons, and their methodology makes facing them an especially frustrating ordeal.

“They play out of a two-shell defense more than anyone in the league,” Shanahan noted. “Even when you get past the front seven, it’s tough to get past those safeties. Those safeties back up everybody for big plays – yet they’re still very aggressive, so it doesn’t feel like you can dink and dunk them the whole game.”

Macdonald has constructed his defense to reap the benefits of a bend-but-don’t-break philosophy without conceding anything meaningful. The result is a unit that suffocates opponents rather than giving them room to operate.

Seattle’s zone-match coverage system delivers the best of both worlds. The resilient two-high shell prevents deep completions, while the “match” component keeps defenders glued to routes. Even seasoned observers struggle to distinguish between their man and zone looks. From snap to whistle, it often appears they’re deploying both simultaneously.

This defensive approach excels at controlling the middle of the field and the seams. Linebackers and safeties occupy these areas, ready to converge on receivers entering their zones. Passing windows shrink rapidly against Seattle’s scheme.

Breaking down these compacted windows requires precise execution, which is where Shanahan’s play design becomes crucial. Purdy’s seamless fit within the system stems from his willingness and ability to fire throws into tight spaces—a skill set that demands anticipation and touch more than raw arm strength.

Shanahan leverages Purdy’s strengths by frequently employing high-low concepts across the middle. One receiver runs a short route roughly five yards deep, while another executes a deeper pattern that curves behind the initial route 10 to 15 yards downfield.

Shanahan’s expertise lies in repeatedly running the same concepts from varied formations and personnel packages to keep defenses guessing. Against 30 other teams, Purdy can target that intermediate middle area consistently throughout games. Since the start of the 2025 season, approximately 25% of his pass attempts have been directed at this five-to-20-yard range between the numbers.

Courtesy of Pro Football Focus.

However, when facing Seattle, that targeting percentage drops to just 12%.

The disparity in production tells the story. According to Pro Football Focus, Purdy averages 5.8 yards per attempt and -0.88 expected points added per play against Seattle. Against other opponents, he averages 9.7 yards per attempt and 0.45 EPA per play. Even when opportunities arise, the Seahawks neutralize them.

During last season’s three games against Seattle, Purdy averaged just 5.8 yards per attempt on structured plays—that’s nearly three yards below his average against other opponents. Forced into scramble mode as the 49ers found themselves trailing, the outcome didn’t improve. San Francisco isn’t built for extended dropback passing situations, though they can manage when necessary. Seattle’s defense makes that approach nearly impossible.

Brock Purdy and the 49ers were dominated in the NFC Divisional Round by the Seahawks earlier this year. (Sean M. Haffey/Getty Images)

San Francisco went without scoring a touchdown over their final 120 minutes against Macdonald’s defense last season, making it imperative that they avoid repeating that pattern. Their first meeting, however, pointed toward a viable strategy for offensive success.

Though the 49ers only managed 17 points in that game, their offense moved the ball effectively. They punted just twice, though mistakes ultimately proved costly—Purdy threw two interceptions attempting difficult throws over the middle, and kicker Jake Moody missed two field goals (including one that was blocked).

Despite the turnovers, Purdy recorded an impressive 85.5 QBR, marking his third-highest total of the season and his second-best performance against a Macdonald-led defense.

While Shanahan’s ground game wasn’t exceptionally efficient, it remained functional enough to prevent abandonment. The running backs accumulated 31 carries, allowing the offense to maintain its preferred tempo and script adherence.

San Francisco’s offensive health often correlates with their shotgun usage rate. In their two losses to Seattle and during Purdy’s three-interception game against Carolina, that figure exceeded 80%. Conversely, when it falls to 75% or lower, the offense typically operates at peak efficiency. In their Week 1 victory, Purdy operated from shotgun on just 74% of his dropbacks—matching that same ratio in the 2024 win that produced 30 points against Macdonald’s defense before it reached its current level of refinement.

Looking ahead to 2026, Shanahan will ideally push that shotgun percentage even lower. The veteran play-caller has incorporated several innovative elements into his offense, many of which feature Purdy operating under center.

Shanahan has revitalized his rushing attack with fresh motion concepts and formations. The result blends traditional aesthetics with contemporary functionality. On one play, fullback Kyle Juszczyk shifts into an old-school split-back alignment just before the snap, setting up a counter concept reminiscent of Bill Walsh’s classic playbook.

Younger coordinators like Bears offensive coordinator Ben Johnson, Buccaneers OC Liam Coen, and 49ers offensive line coach Klayton Adams have advanced run-game innovation significantly. Shanahan refuses to fall behind. He could rest on his proven “A Million Different Ways to Run Outside Zone” philosophy, but he understands that sharp defensive minds like Macdonald continuously evolve.

Macdonald’s run defense has undergone substantial transformation since his rookie season in Seattle. Last year’s loss to San Francisco—one that saw the 49ers rush for 228 yards—appears to have catalyzed change. In response, Macdonald integrated more run blitzes to close gaps previously exploited by opposing offenses. The upcoming matchup showcases defensive evolution at its finest.

What initially appears to be an inviting C-gap before the snap…

… gets sealed shut by a blitzing defender immediately after the snap.

The numbers back this evolution. In Macdonald’s inaugural 2024 season, Seattle deployed run blitzes on only 13% of running plays. That figure climbed to 23% in 2025 and now stands at nearly 30% in 2026.

Sunday’s strategic battle between Shanahan and Macdonald will likely be decided in the trenches. Shanahan will seek soft spots along the line of scrimmage, while Macdonald works to conceal them. It’s essentially a high-stakes game of “Battleship” played with 300-pound athletes instead of plastic pegs.

If Shanahan wins that tactical war up front, Purdy should operate at his highest level and position himself for another exceptional performance—one that strengthens his position as the frontrunner for league MVP. More significantly, such a victory would give the 49ers a commanding two-game lead in their division and establish them as the NFC’s premier team.

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