The 49ers are running into the stingiest defense in the NFL

The San Francisco 49ers are looking for a perfect first leg against the NFC West with a win on Sunday in the Pacific Northwest against the Seattle Seahawks.

After defeating the Rams and Arizona, the 49ers sit atop the NFC West, but the 3-1 Seahawks are within shouting distance, and an early division lead is on the line. A win would give San Francisco the tiebreaker over all three NFC West foes in the early goings and a two-game lead in the win column.

But Seattle was a tricky game (twice) in the ladder half of 2025 for the 49ers, and Sunday could be the same with Seattle getting Sam Darnold back a couple of weeks ago. And while Darnold will lead the Seattle offense, the main attraction of the Seahawks is that defense.

Let’s take a closer look at the Seattle defense with this week’s numbers to know:

Yards per game. The Seahawks defense allows 246.8 yards per game, the best in the league.

The Denver Broncos defense was just a Week 4 appetizer for the Week 5 main course: Mike Macdonald’s elite Seattle defense.

Entering Week 5, only two defenses have allowed fewer than 1,000 yards. After Sunday, the 49ers will have played both of those teams. The 49ers offense put up 379 yards in Week 1 against the Los Angeles Rams, the current season-high against Los Angeles, but since then, the Rams have allowed 611 in three games, bringing their season total to 990 yards allowed. Only one team has allowed fewer yards: the Seahawks.

While the 49ers offense has gained more than 300 yards in all four games this season, Seattle has allowed more than 300 yards once, last week when the Los Angeles Chargers gained 301. And just as the 49ers’ ability to gain yards has led to the second-highest point output through four weeks (122), Seattle’s ability to hold offenses has kept teams to the fifth-fewest points (73).

In simpler terms, Sunday will be an immovable object versus an unstoppable force.

Now, where will the 49ers find the firepower against Seattle’s defense? Mike Evans is banged up, and unlike Week 1, the 49ers will be without Demarcus Robinson and De’Zhaun Stribling. The receiver injuries will be familiar, though, as the position group was hurt last season when Seattle dominated the 49ers offense in Week 17 and the playoffs.

Touchdowns. The Seattle defense has allowed one rushing touchdown this season, the second-fewest allowed in the league.

While the passing game has been responsible for 11 of the 49ers’ 16 touchdowns this season, Christian McCaffrey on the ground remains the biggest scoring threat on the 49ers’ offense, especially inside the red zone.

Seattle’s defense has been susceptible to the run this season, allowing 100+ rushing yards in two of its four games. But because Seattle is so good everywhere else on defense, that slight issue against the run hasn’t hurt much.

But this game might be decided by how often the 49ers offense can get into the red zone. Seattle has allowed the second-fewest red zone entries with nine through four games. Despite the few entries, Seattle has allowed five touchdowns, a 66.7 touchdown rate tied for the tenth-highest.

Only one of those red zone touchdowns has come on the ground. And that’s where McCaffrey comes into play. All 27 of his rushing touchdowns have come inside the red zone, and all four of his rushing touchdowns in 2026 were one-yard scores. It’s safe to say that Seattle’s defense won’t face a red zone weapon like McCaffrey outside the two games against the 49ers.

It’s tough to move the ball against Seattle’s defense, and it’s especially hard to score on the ground. McCaffrey could be the answer to that threat.

Record. The 49ers are 7-3 (including playoffs) against the Seahawks under Brock Purdy.

If Purdy can continue his current form against this Seattle defense, it would be a statement game we look back on to solidify an MVP case at the end of the season.

Purdy did have his struggles against the Seahawks in 2025, averaging 181.3 passing yards in three games against Seattle, in a season where he averaged 240 yards per game. Even after success in his first try against Macdonald’s version of the Seahawks when Purdy threw for three touchdowns leading a 49ers win, all three of Purdy’s losses to the Seahawks have come under Macdonald’s tenure.

But that doesn’t mean Purdy hasn’t had success against Macdonald. Purdy has led the 49ers to two wins against Seattle and has looked good in both. The first being the aforementioned three-touchdown game from Purdy, picking up a win in Week 6 of the 2024 season, but he also led the game-winning drive in Week 1 last season, capping off a two-touchdown day.

Purdy’s dominance of the Seahawks was more of a Pete Carroll thing than it was a Macdonald. And while the Seahawks’ head coach has had Purdy’s number dating back to Christmas Day 2023, Purdy has had his fair share of success as well.

Sunday, however, Macdonald and the Seahawks defense will have to face Purdy in the middle of one of the best stretches of his career.