Arik Armstead might be unsung in NFL, but 49ers know his...

Ask someone about the NFL’s No. 1-ranked defense, and you’re likely to hear a handful of names responsible for the 49ers’ success before defensive lineman Arik Armstead is mentioned.

Unless the question is posed in Santa Clara.

Inside the walls of Levi’s Stadium, it’s widely understood that Armstead is a key reason why the 49ers have allowed a league-low 248 yards per game and piled up an NFL-best 44 sacks.

“He’s playing All-Pro, legitimate All-Pro football, week in and week out,” 49ers cornerback Richard Sherman said. “Whether it’s prime-time games or games nobody’s watching, he’s out there making an incredible impact. He’s putting guards into the quarterback’s lap. Tackles into the quarterback’s lap. Tight ends. Whoever. Everybody can get it. He’s the can man. Anybody can get it.

“Whoever lines up in front of Arik Armstead is going to have a long day.”

There’s plenty of credit to go around in the 49ers’ attacking defense that has propelled the franchise’s surprising rise to the top of the NFC standings.

There’s defensive coordinator Robert Saleh, who has solidified himself as one of the league’s hottest names for head-coaching vacancies. There’s Sherman, the defensive captain, who brought a Hall of Fame swagger and winning culture from Seattle.

There’s All-Pro defensive tackle DeForest Buckner, rookie sensation Nick Bosa and reigning NFC Defensive Player of the Week Fred Warner.

Eventually the conversation flows to Armstead, who has a team-best 10 sacks for a unit that has recorded at least three sacks in eight straight games.

“I think they said he’s at 10 sacks now? On a contract year?” Sherman said. “I mean, the Brink’s truck is going to back up. Beep. Beep. I can’t wait. I’m excited for him. Hopefully, he gets the credit he deserves.”

Armstead is making $9.05 million in the fifth year of his rookie contract, a number that seemed quite steep after an injury-plagued and unproductive start to his career. The 6-foot-7, 292-pounder, picked 17th overall out of Oregon in 2015, recorded just nine sacks in his first four seasons combined.

He finished the 2016 and ’17 seasons on injured reserve, having played in just 14 of 32 possible games during the stretch. The 49ers maintained that Armstead was doing his job as the edge-setter in run defense, but he was having minimal splash impact.

Even as he made it through an entire 16-game season last year, Armstead had just 12 quarterback hits, six tackles for a loss, and zero forced or recovered fumbles. It’s taken him just 11 games this season to rack up 13 quarterback hits, 10 tackles for a loss, two forced fumbles and a fumble recovery.

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How does he explain it?

“Oh, man, just playing as hard as I can,” Armstead said. “Being put in good situations. Being surrounded by great players. Working hard. Working on my craft. Fighting through adversity throughout my career. Having support from my family and my fiancee. There’s a lot that goes into it.”

Armstead was well aware that people were questioning his rash of injuries and counting him among the league’s many busts. Instead of listening to the critics, Armstead decided to “put my head down and grind.”

Actually, that’s almost exactly what defensive line coach Kris Kocurek demands of Armstead.

In the 49ers’ new Wide 9 alignment, Armstead is often lined up outside the opponent’s tight end, allowing him to crash into the backfield. Last year, he was generally positioned as a six technique, tasked with lining up directly over the tight end and engaging the blocker while trying to read the play.

Armstead described it more simply when he said he now gets to play “vertically” as opposed to “horizontally.”

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“Sometimes being the smartest D-lineman in the room can backfire on you, especially if you have gray area in the way you’re seeing things,” Saleh said. “Arik has completely bought into a style that coach Kocurek, and really everybody in this organization, believes he can be, and it’s showing up play-to-play. He’s playing exactly the way he’s being asked to play, and he’s showing his dominance.”

Especially when the game is on the line.

Sunday’s game Who: 49ers (10-1) at Baltimore (9-2) When: 10 a.m. TV: Channel: 2Channel: 40 Radio: 104.5, 680, 107.7

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Trailing 20-17 midway through the fourth quarter of the Week 3 game against Pittsburgh, Armstead crushed running back James Conner from behind and forced a fumble that sparked the 49ers’ 24-20 win.

Trailing 26-23 in the final four minutes of the Week 9 game against Arizona, Armstead engulfed quarterback Kyler Murray for a sack that ended the Cardinals’ drive and fueled the 49ers’ 28-25 victory.

“He’s ballin’ right now, and it’s just great to see,” Buckner said. “He’s definitely had some adversity throughout his career. Just to see him having the season he’s having right now, it’s finally coming all together for him.”

Rusty Simmons is a San Francisco Chronicle staff writer. Email: rsimmons@sfchronicle.com Twitter: @Rusty_SFChron