SEATTLE — The Seattle Seahawks left Green Bay last Sunday surprised, not so much that they lost — no one figured a win at Lambeau would come easily — but in the way that defeat happened.

An offense that led the NFL in the preseason in total yards — standing in the top four in both rushing and passing — was held to its fewest yards (225) in a regular-season game in almost three years and just three field goals as the Packers pulled away late for a 17-9 win.

“You could not have convinced me going into that game that that was the way we were going to perform,” said offensive coordinator Darrell Bevell. “We’ve performed really well here in practice against a great defense out here in training camp. We performed well in the preseason. So I was convinced that we were going to go out and have a real solid game. But it was one of those first games, and we made some mistakes.”

That’s the hope, anyway, that it was just one of those days against a good team on the road, an offense with some new parts still needing to find itself.

“I have no doubts that we will be better, that we will improve and we will get better in all the areas,” Bevell said. “Usually the second game, obviously from the first game, you correct a lot of things. I have no doubts that we will be able to do that.”

If that doesn’t happen Sunday when the Seahawks take on the San Francisco 49ers, though, then the doubts about this team and season will not only increase in intensity but take on added validity.

Struggles at Green Bay are one thing. But the 49ers, once Seattle’s most heated rival, have instead been the Seahawks’ biggest punching bag the last few years, the team to see when the patient has felt a little ill.

Seattle has won its last six regular-season games against the 49ers by a combined 147-67, and the last four have come the week after a Seahawks loss.

In 2015, the Seahawks beat the 49ers 20-3 four days after a stunning last-second loss to Carolina and then 29-13 after an almost equally stunning home defeat to Arizona.

Last season, the Seahawks beat the 49ers 37-18 in Seattle a week after a desultory 9-3 loss to the Rams, then closed out the regular season with a 25-23 win in the Bay Area after a home defeat to the Cardinals knocked the Seahawks out of the number-two playoff seeding.

And typically the Seahawks have beaten the 49ers by getting back to basics, averaging 160 yards rushing in those four wins.

Of course, the past might not mean much given that San Francisco is working on its fourth head coach in four years. Kyle Shanahan is installing the offensive system that he coordinated in leading Atlanta to the Super Bowl last season. He hired former Seahawks assistant coach Robert Saleh to bring in a defense similar to Seattle’s.

But the 49ers still appear as beatable, if not also as bendable, as any team on the Seahawks’ schedule, having lost 18 of their past 21 games and a year ago setting team records for defensive futility. San Francisco allowed an NFL-most 2,654 rushing yards last season as well as an NFL-high 4.8 yards per carry.

The 49ers looked better on defense last week, allowing just 116 rushing yards to Carolina on 38 carries, 3.1 yards per attempt, in a 23-3 loss.

Still, if the Seahawks can’t get the running game going at home against the 49ers with projected starting tailback Thomas Rawls back in the fold, it will be fair to ask when they will get it going.

The Seahawks felt they didn’t have enough chances to establish the running attack last week with just 15 called running plays and only 18 runs overall, good for 90 yards, with 40 of them coming on two Russell Wilson scrambles.

“We just need to keep doing it,” coach Pete Carroll said this week. “Keep chopping wood is really what it takes.”

But the Seattle offensive line will also have to level some 49ers defenders to make that happen.

The offensive line did nothing against Green Bay other than raise fears that it could again be the weakest link on the team.

Offensive-line coach Tom Cable, often the biggest public defender of his players, didn’t skirt the issue this week, saying simply “not good enough” when asked how the line played against Green Bay.

Carroll said the same for the whole team, noting that while the defense kept the Seahawks in the game it also couldn’t stop Green Bay from running off the last 6:17 after Seattle closed to 17-9, or stop the Packers from converting 9 of 16 third downs.

“We have high standards, and we didn’t meet it last week and our guys are determined to get back on track,” Carroll said.

They always have lately against the 49ers, the get-well card that the Seahawks hope again delivers.