This is the game the 49ers have had circled on their calendar since the moment the schedule dropped.

This is their shot for revenge. This is their chance to prove that they are, in fact, still the top dogs in the NFC West and, ergo, the NFC on the whole. Which, one could argue makes them the team to beat for the whole league.

This team wants nothing more than to march into Seattle, kick the doors down and take their souls back.

Souls?

I’m just following Kyle Shanahan’s lead here. Remember when he stood on the field before Super Bowl LX and, looking dead-eyed into an NBC camera, said as much?

“I know you guys want my expert opinion, but I haven’t scored a touchdown on (the Seahawks) the last two times we’ve played them, so I don’t know how good that is.”

Here’s the good news: I think they’ll score a touchdown this week.

Beyond that, however, I have little optimism to proffer. (Shocker, I know.)

Seattle’s defense under Mike Macdonald remains San Francisco’s schematic kryptonite.

You can say things like: “Seattle sits in two-high all game” or “they only run zone defense” or “they don’t have a bona fide, sack-getting edge rusher,” and you wouldn’t be lying.

And against any other team, those things would make you lean toward the 49ers.

Two-high defenses? Time to run the ball.

Zone defense? That’s what Shanahan was put on the planet to exploit in the pass game.

No Will Anderson or Nick Bosa knockoff? Brock Purdy is about to carve these boys up.

But this is Seattle’s defense, and what could be perceived as weaknesses are, in fact, strengths.

They’re in two-high because they want you to run the ball into their preposterously good defensive front that is, frankly, breaking some of the mainstream statistical models.

They play zone because between pressing receivers at the line of scrimmage and passing things off with a shocking crispness, they take away all the zone-beater concepts you would run against them. It’s effectively man coverage, save for the fact that you don’t know which man is covering when the ball is thrown. Not ideal!

And the lack of a sack-getter? Well, I hope you have your head on a swivel, because the Seattle defensive line always collapses the pocket, and they will attack with free-run blitzers from anywhere and everywhere. They break offensive line rules with precision.

The 49ers might have the best offense in the NFL early this season, but Seattle’s defense remains the single best unit in the NFL and a generational one, at that.

And while there is certainly a world where Shanahan and Purdy are able to create the kind of magic that neutralizes that defense — I think they know what they’d want to execute — the current state of the Niners’ receiver room and the lack of fullback Kyle Juszczyk make me believe we are not currently living in it.

To be abundantly clear, I want to be on that planet. I don’t root for one team or another, but the reason I love football is the tactical battles — the chess match between great players and great coaches. The game is always evolving, and that evolution creates mental and physical challenges that no other sport can match.

And if Shanahan can find a second way to beat Seattle’s defense — one that his current roster can actually execute — it would be a huge leap forward in the game. The proverbial ball would be kicked back into Macdonald’s court. Now we have action.

Last year in Week 18 and the divisional round, there was no action, only domination.

I’m expecting a more competitive game, but the same outcome.

Anywho, here are some specific predictions:

Prediction 1: Brock Purdy takes his first sack of the season as Seattle overloads the interior

Isn’t this a brave prediction? Wow, what a football mind I am.

But this prediction, as pedantic as it is, really does matter. Through the first four weeks of the season, Purdy has been the dot at the very top right of every advanced efficiency chart. He’s getting the ball out on time, anticipating windows, and the 49ers offensive line has given him just enough time to make it all happen.

But this isn’t the Dolphins or the Cardinals.

And we saw some cracks in the facade last week against the outside-pressing Broncos.

Seattle, I hope you’ve picked up by now, doesn’t play standard, Robert Saleh landmark zone, which would let Purdy sit in the pocket reading the safeties and delivering balls to anywhere he wants on the field.

Instead, Seattle leans on simulated pressures and the trendy (though they’re the trendsetters) B-gap overload blitz, bringing four rushers to one spot on the line while showing seven or eight eligible bodies, forcing the offensive line to slide into an impossible guessing game.

That spells disaster for left guard Connor Colby — who has been up and down in pass protection this season. They’re going right at him with two or three bodies on Sunday.

Shanahan’s protection schemes often leave a rusher to Purdy’s blind side while he throws “hot” to the perimeter, similar to how a read-option run play works. Shanahan believes that the answer is always in the play, and Purdy is incredible at creating enough time to find it in those one-on-one situations on the end.

Free interior rushers are a different story.

The answer might be in the play, but can Purdy see it in time to make that play? This has been Purdy’s one overt weakness throughout his sterling NFL career — he can do so many things, but he can’t make himself 6-foot-5 and 230 pounds.

Add in the lack of separation the current slate of Niners receivers (save for, but also kind of including the banged-up Mike Evans) has shown lately, and you have No. 13 running a lot and going down a few times.

And since we haven’t seen that yet this season, I have to question how San Francisco responds to that kind of drive-killing play.

Prediction 2: Rashid Shaheed and JSN exploit San Francisco’s deep safeties on play-action shot plays

Here’s a positive: The 49ers’ defensive front can get after Sam Darnold in this game, and credit to defensive coordinator Raheem Morris for that.

Because of injuries, he has a weird group up front, and he’s matched that weirdness in his scheme. Add the idiosyncratic but dominant Mykel Williams to the mix, and Morris has a shot to do some really cool stuff this week.

That said, if the Niners don’t get Darnold, he does have the kind of arm that can make you pay.

Seattle will combat San Francisco’s front-seven (eight?) aggressiveness by leaning into perimeter pitch tosses, wide receiver backfield sets and half-rollouts that move Darnold off-platform and buy extra seconds for vertical routes to develop.

That creates a nightmare scenario for San Francisco’s safeties. The tandem of Ji’Ayir Brown and Malik Mustapha lacks true free-safety range and deep recovery speed.

Brown has an aggressive trigger against the run and play-action, making him chronically susceptible to taking the bait in the backfield, but also biting on double moves.

With Jaxon Smith-Njigba on the field, that’s a real problem. And if the Niners bracket JSN, well, then Seattle offensive coordinator Brian Fleury can dial up a deep vertical shot for Rashid Shaheed out of a play-action look. It might even be a play-action look to Shaheed himself. Don’t sleep on Tory Horton, either. He’d be the Niners’ second-best receiver right now.

I think the big shots will be there for Seattle, and that will be the difference.

Prediction 3: Kaelon Black hits on a counter run

You cannot run pure outside zone against Seattle. But you might be able to hit them with gap-scheme runs.

Without Juszczyk being a one-man gap scheme, look for Shanahan to motion George Kittle into the backfield more to serve as a wrinkle in the run game and an offset lead blocker to mix it up from tight ends and honorary fullbacks Luke Farrell and Brayden Willis this week.

Furthermore, while McCaffrey will remain the engine, Shanahan has been setting up rookie running back Kaelon Black for this game.

Black possesses the reckless abandon great zone rushers avoid. That’s perfect for a gap-scheme staple: counter.

It’s dangerous to pull linemen in the run game against Seattle — it’s boom or bust — but what choice does San Francisco have in this game? The Niners have to play for the big shot, because their short and intermediate staples in the pass game won’t be there against this defense. The zone-run staples won’t be available, either.

I don’t expect the Niners to break off a 50-yard home run with counter, but I think Black — who is seeing it better in recent weeks — hits a big run or two in this game off that concept.

Final Score: Seattle Seahawks 18, San Francisco 49ers 13

San Francisco’s defense will battle valiantly and generate disruption, but Shanahan’s banged-up offense can’t go man-for-man with Seattle’s defense right now, and the absence of Juszczyk undercuts the Niners’ run game, forcing Purdy to play Superman. He’s exceptional, but I think that’s too tall a task for a shorter quarterback like him.