The San Francisco 49ers walked off the field Sunday with a 24-14 victory over Denver and a 4-0 record.

But behind that perfect start lurks a brutal, recurring, nearly tragic nightmare: The 49ers thought they solved their Seattle problem in the offseason. Now they’re beginning Week 5 staring directly into the exact same tactical ditch.

Seattle beat the Niners twice in January by playing bully ball: big pressure up front, clamping down in press-match coverage, taking away the middle of the field and daring the 49ers to win a physical game on the perimeter.

The Niners spent the spring counter-punching. The 2026 edition of the 49ers’ offense was supposed to be a philosophical evolution.

Bring in Mike Evans, lean on Ricky Pearsall, and swiftly develop rookie De’Zhaun Stribling. Give Brock Purdy perimeter wins so Kyle Shanahan can borrow Sean McVay’s Rams playbook (29 points per game against the Seahawks last year) and hit Seattle with successful gap-scheme runs and a pass game of five- and seven-step dropbacks with deep rips down the field.

It was developing quite nicely, even without Pearsall and then Stribling. Going into Week 4, no team had run less play action than the 49ers. No quarterback was playing better than Purdy, who was playing like his idol, Dan Marino.

But to keep running that offense, you need those man-to-man beaters on the outside.

As we saw against the man-heavy Broncos Sunday, the Niners don’t have them anymore.

It’s a repeat of 2024 and 2025. The 49ers are right back where they started.

Pearsall remains sidelined, Stribling isn’t walking through that door — he’s scooting around with his surgically repaired ankle — and Evans, a warrior, was audibly creaking on the All-22 film.

Against Denver, Evans gutted his way through cracked ribs, a bad hip and a bad foot, dragging himself to five contested catches. Over eight targets, he generated a microscopic 1.95 yards of separation — and that includes three wide-open looks that Shanahan schemed open. He’s in overt pain on the field, a shell of the player we saw in the first few weeks of the season.

When your vertical man-beater looks like he just crawled out of a rollover accident, you don’t have an explosive passing attack.

And without Evans in even close to medium health, the Niners don’t have anyone who can win man-to-man.

We saw the problems against Denver.

Purdy has candidly admitted he only sees downfield receivers cleanly about 40% of the time. That’s the problem when you’re 6-foot-1 — if that. When interior pressure caves the pocket into his face, those throwing lanes don’t just shrink; they vanish.

And when you can’t see your receivers and you don’t trust them to have space on their marks, well, you end up scrambling a lot.

That worked against the Broncos — though it took both of their elite cornerbacks being injured for the Niners to start moving the ball through the air.

It probably won’t work against the Seahawks.

Seattle’s defensive front was assembled specifically to create that exact kind of interior panic. Their secondary loves to play pinball with receivers off the line of scrimmage.

Frustrating, isn’t it?

At least they have the run game, right?

Well, about that …

A sledgehammer hit that idea on Monday when Shanahan announced that fullback Kyle Juszczyk won’t play against Seattle after hyperextending his knee against the Broncos.

The news of a looming absence was expected, to be sure, but the impact will be significant.

Losing Juice isn’t just losing a fullback; it’s tearing down the load-bearing wall of the Niners’ run architecture.

The Niners’ run game looks almost nothing like the famous stretch outside-zone scheme that lifted them to a Super Bowl berth in 2019.

It was forced to evolve. But ever since Shanahan unleashed dash motion against Atlanta in Week 7 of 2025, Juszczyk has been a tactical cheat code. By flying across the formation at the snap, Juice changes gap counts in real time, breaks front-seven fit rules, and gives Christian McCaffrey daylight.

Brayden Willis is an admirable football player, but Willis isn’t Juszczyk. Not even close. He isn’t even the preferred fullback backup — that was Jake Tonges, who was lost for the season in Australia.

The Niners wanted to have strong gap-run jabs to set up their deep downfield passes this season. This was all done with Seattle in mind.

Now they might have neither of those options — you need Jimmys and Joes to execute the X’s and O’s.

Yet amid the triage, an undeniable window for reinvention exists.

Shanahan didn’t build a decade-long reputation as an offensive guru by hyperventilating when Plan A snapped.

But this Week 5 matchup demands genuine lab-cooked invention, not just clever play-calling.

Who will provide that invention?

Brian Fleury, the former 49ers assistant who originally drew up dash motion — Shanahan’s big ideas guy, following in the footsteps of Mike McDaniel — is now Seattle’s offensive coordinator.

So who is the ideas guy in Santa Clara right now?

Who is the assistant staying up until 3 a.m. on a Tuesday, digging through obscure Sun Belt tape to find a run concept that breaks Mike Macdonald’s defensive rules?

Is it offensive coordinator Klay Kubiak? Someone deeper on the roster?

Whoever it is, they have their work cut out for them this week.

Someone in that offensive meeting room needs to brew fresh coffee and start drawing, because rolling up to Lumen Field with a battered receiver corps and a stopgap option at fullback, running the same stuff you practiced all summer, is asking for an ambush.

San Francisco circled this game the second the league dropped the schedule. The NFC West rivalry has reached its tactical boiling point, but Seattle holds the advantage.

The 49ers spent nine months engineering an antidote. Then the vial that contained it exploded.

And by kickoff Sunday, we’ll find out if the Niners crammed well enough to pass the test.

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