Aaron Donald’s 2.5 sacks against Seattle give him season-best 12.5 ... with six games to go

The Seattle Seahawks sliced through the Rams defense like a warm knife through butter on their first two series Sunday, rushing for 104 yards and scoring two touchdowns.

“Very embarrassing,” said defensive lineman Ndamukong Suh.

So when Seattle got the ball for a third time to start the second quarter, Suh said someone had to step up. And tackle Aaron Donald did, tackling Seattle’s C.J. Prosise for a three-yard loss and sacking quarterback Russell Wilson on consecutive plays, forcing a punt and turning the tide of a game the Rams would go on to win 36-31.

Donald had two other big plays that came in the waning minutes, joining Suh to bury Wilson on a third-down sack and then hurrying the Seattle quarterback into an incompletion on the Seahawks’ final play. And while that sealed the victory, it did little to smooth over the jagged edges of a second straight rough effort by the Rams defense.

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Rams linebacker Dante Fowler forces a fumble on Seattle Seahawks quarterback Russell Wilson in the fourth quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams’ Aaron Donald falls on Seattle Seahawks quarterback Russell Wilson while trying to recover a fumble in the fourth quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams receiver Brandin Cooks is lifted into the air by Rodger Saffold after scoring a touchdown against the Seahawks in the fourth quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams receiver Robert Woods stiff-arms Seattle Seahawks safety Delano Hill to pick up yards in the third quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams quarterback Jared Goff scrambles for yards against the Seattle Seahawks at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams tight end Tyler Higbee scores a touchdown against Seattle Seahawks cornerback Justin Coleman in the fourth quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams defensive tackle Aaron Donald sacks Seattle Seahawks quarterback Russell Wilson in the second quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams running back Todd Gurley scores a touchdown in front of Seattle Seahawks defensive end Dion Jordan in the second quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams running backs from left, Todd Gurley, Malcolm Brown and Justin Davis walk to the field before a game with the Seattle Seahawks at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Seattle Seahawks tight end Nick Vannett catches a touchdown pass in front of Rams safety John Johnson in the first quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

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Rams receiver Brandin Cooks picks up yards as Seattle Seahawks safety Tedric Thompson leaps over receiver Robert Woods to try and make a tackle in the second quarter at the Coliseum on Sunday.  (Wally Skalij / Los Angeles Times)

“We’ve got to settle down, understand what teams want to do against us early in the game,” Suh said. “We found a way to come back. We’ve got to find a way to do it faster.”

They’ve got to find a way to do it cleaner too. Because for all of Donald’s heroics — he finished with five quarterback hurries and 2½ sacks, giving him a career-best 12½ sacks for the season — costly mistakes by teammates almost gave the game away.

The Rams defense was penalized six times for 78 yards, most of them proving costly. On Seattle’s opening possession, a third-down roughing penalty on Cory Littleton extended the series and a facemask penalty on Dante Fowler Jr. helped set up a Seattle touchdown. And on the Seahawks’ first drive of the second half, a holding penalty on Marcus Peters wiped out an interception and a post third-down unsportsmanslike-conduct foul on Fowler led to another Seattle score.

But Fowler, a former first-round draft pick playing his second game for the Rams, was able to make up for that disastrous play by sacking Wilson midway through the final quarter and forcing a fumble that he recovered. One play later the Rams scored.

“I knew I had to put the team on my back,” Fowler said. “I had to go out and redeem myself and show the coaches that they can trust me to go out there and make big plays.”

Still, he left the Coliseum more frustrated by the penalty — which he said came from arguing with an official — than he was excited over the fumble recovery.

“It’s definitely a learning experience,” he said. “It was a third down and I kept them on the field. And they got points off of that. I’ve got to be very smart.”

When asked what he learned, Fowler replied “don’t talk to referees.”

The penalties and the poor first period weren’t the only blemishes in a defensive effort that was nonetheless an improvement over a week ago when the Rams gave up a season-high 45 points and 487 yards in a loss to the New Orleans Saints.

Seattle’s Rashaad Penny ran for 108 yards and a touchdown, and Wilson — when he wasn’t being sacked; he went down four times — scrambled for 92 yards in nine carries. But the Rams held when they had to, stopping the Seahawks on seven of nine third downs and forcing the game’s only turnover.

That served as a loud response to Seattle guard D.J. Fluker, who questioned the physicality of the Rams defense after the teams met in Week 5. Fluker missed Sunday’s game because of a calf injury.

“Seattle is a team that wants to come in and impose their will,” Suh said. “And we’re a team that doesn’t really allow those things.”

At least not when Donald’s in the opposing backfield. Over the last two seasons, the Rams are 15-0 in games in which Donald has recorded a sack.

“Just going out there and doing my job and good things happen,” Donald said. “I’ve got great teammates that help me to achieve things like that.”

But they still have a lot to clean up.

“Not pleased at all with the penalties, the self-inflicted wounds. It’s not indicative of the type of football team that we want to be,” said head coach Sean McVay, whose defense gave Seattle five first downs on penalties. “I’ve got to do a better job of making sure that our standards, our expectations, are much higher with regards to how we respond to some of the things that don’t go our way.

“The guys did find a way to win and that’s a credit to their mental toughness. But there was a lot of instances that we have to avoid moving forward.”

kevin.baxter@latimes.com | Twitter: @kbaxter11