Seahawks vulnerable to sacks just as 49ers become more proficient

Recommended Video:

On the first play of last season’s NFC Championship Game, 49ers outside linebacker Aldon Smith sacked and stripped Seattle’s Russell Wilson and recovered the fumble.

Ten months later, the stage could be set for a similar plays Thursday night when the 49ers host the Seahawks, who allowed a season-high seven sacks in a 19-3 win against Arizona on Sunday. The Cardinals finished with 11 tackles for losses against Seattle’s patchwork offensive line, and Arizona head coach Bruce Arians thought their sack total could have been even higher.

“Seven sacks is a nice day,” Arians said, “but when you miss four more, it could’ve been a huge day.”

Seattle was without two season-opening starters against Arizona — center Max Unger and left guard James Carpenter — because of ankle injuries. Carpenter is expected to play Thursday, but Unger will likely remain sidelined.

Seattle head coach Pete Carroll acknowledged the Seahawks have issues to correct before meeting the 49ers, who matched a season high with five sacks in a 17-13 win over Washington on Sunday.

An encore of Aldon Smith’s fumble-inducing playoff sack of Seattle’s Russell Wilson (3) seems plausible on Thursday. An encore of Aldon Smith’s fumble-inducing playoff sack of Seattle’s Russell Wilson (3) seems plausible on Thursday. Photo: Elaine Thompson / Associated Press Photo: Elaine Thompson / Associated Press Image 1 of / 1 Caption Close Seahawks vulnerable to sacks just as 49ers become more proficient 1 / 1 Back to Gallery

“We had all kinds of problems,” Carroll said. “We got beat one-on-one, we had some scheme issues, and we held the ball too long. To have that kind of an onslaught, it took a lot of stuff.”

On Sunday, Patrick Lewis made his second career start in place of Unger. Lewis entered the NFL in 2013 as an undrafted free agent and has been on the rosters of four NFL teams, an odyssey that includes two stints with the Seahawks and Browns.

Carroll said he wasn’t sure Lewis would start against the 49ers. Seattle’s other option is Lemuel Jeanpierre, who has made eight starts in his four-year career.

“We will find out,” Carroll said. “We will let these guys battle again this week. Lemuel will be a week older with us this time around. We will see how it goes.”

Brilliant backfield: Defensive coordinator Vic Fangio isn’t prone to hyperbole, so it was notable when he offered a particularly glowing assessment of Seattle’s backfield.

Led by running back Marshawn Lynch and quarterback Wilson, Seattle ranks first in the NFL with 169.6 rushing yards per game. Lynch ranks fifth in the league in rushing (852 yards), while Wilson ranks 15th (644) and is averaging 7.7 yards a carry.

“They’ve got Marshawn Lynch, who, if he’s not the best back in the league, he’s second to somebody,” Fangio said. “And then you’ve got Wilson back there, who could pull the ball at any time and become a runner himself … When Wilson has the ball in his hand, he’s like defending Barry Sanders, with his quickness, and elusiveness and speed.”

Eric Branch is a San Francisco Chronicle staff writer.