SEATTLE — The question “How have the 49ers beaten the Seahawks recently?” could prompt a book as much as a column.

Once the fiercest rivalry in the division — if not the conference — the lopsided nature of this matchup over the past two seasons equates to Joey Chestnut vs. hot dog.

San Francisco has won the past five games against the Seahawks, with the closest margin being eight points and the average being 15.2. The Niners have dominated Seattle on just about every front and at every position.

But there is one area in which San Francisco’s supremacy has been particularly salient — in the trenches. Especially on the offensive line.

And it begs the question: Have the Seahawks really done much to push back against this? Or is their defensive line as suspect as ever?

This question goes beyond Thursday’s game between these teams at Lumen Field. The defensive front is a space in which the Seahawks have devoted significant resources in recent years, knowing it’s been exploited across the NFL.

Among their moves? Signing linebacker Uchenna Nwosu in March 2022. Trading for defensive end Leonard Williams last October. Signing fellow DE Dre’Mont Jones to a three-year, $51 million contract in March 2023. Drafting defensive tackle Byron Murphy II in the first round of the draft in April. Drafting linebacker Boye Mafe in the second round in 2022 … and so on.

The moves could still pay dividends en masse in the end — and there certainly have been some achievements worth celebrating. Mafe, for instance, had nine sacks last season and at least one sack in seven consecutive games. When healthy, Williams has been one of the more effective players on the entire roster.

But with the Seahawks (3-2) coming off consecutive losses — both of which were the result of defensive shortcomings — how are all those moves working for them now?

Nwosu, who missed most of last season, will be put on injured reserve soon due to a thigh injury. Seahawks coach Mike Macdonald said he thinks there is a good chance he can get the edge player back before the season is over, but the timeline is nebulous for now. Jones, meanwhile, has logged two sacks this season but has a paltry Pro Football Focus grade of 56.6, which is consistent with the run-defense struggles Seattle has experienced for most of the season.

Murphy hasn’t performed much better in his limited time and will miss his third consecutive game Thursday because of a hamstring issue. Mafe has had a sack in the three games he’s played in and has graded well in the analytics crowd — but has also been sidelined the past two games.

The 49ers (2-3) certainly haven’t been the force most expected them to be after taking the Chiefs to overtime in the Super Bowl last season. Not having Christian McCaffrey, likely the best running back in the league, has played a significant role in their shortcomings. But there’s a reason they still sit as 3 1/2-point favorites despite coming to Seattle. They are seen as the more physical team. And if you look at the Seahawks’ past two defeats, they have been lost in the trenches — most notably on the defensive side of the ball.

The Giants racked up 175 yards on the ground on 34 carries in Sunday’s 29-20 win.

The Lions, meanwhile, managed to complete all 19 of their passes the Monday before, all while rushing for 116 yards.

Even the lowly Patriots found a way to amass 185 rushing yards in Week 2 vs. the Seahawks, a game in which a missed field-goal attempt by New England led to an overtime win for Seattle. Over the past couple of seasons, San Francisco’s ground game has been just as lethal.

On Wednesday, Macdonald was asked about the Niners’ recent dominance over the Seahawks up front.

“I can’t speak to last year. I mean we’re talking about the 2024 Seahawks. We got to clean up our run defense. Let’s focus on that,” said Macdonald, in his first season as the Seahawks’ coach. “But they’ve [San Francisco] got a great unit. We’re on record of saying it. We got really good players, let’s go do it.”

The Seahawks’ identity has been difficult to determine through this first third of the schedule. Their wins have come against teams with ineffective (or missing) quarterbacks, and their losses have been marked, in part, by injuries.

But a loss Thursday would redefine a season that was teeming with optimism just a couple of weeks ago. Want to bring that optimism back? Learn to win the game up front.

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