In one of their offseason Zoom meetings, the Washington Football Team’s offensive linemen couldn’t believe what they were seeing. They knew their new position coach, John Matsko, was intense and detail-oriented, but now he was teaching them technique with grainy, black-and-white practice tape from the 1970s. The linemen on screen looked about 250 pounds, smaller than any of them had been in years.

This wouldn’t surprise anyone who knows Matsko. In his 29-year NFL career, he has earned a reputation as one of the league’s top line coaches with a fiery personality, encyclopedic knowledge of old game film and vigorous focus on preparation. He has embraced the unorthodox: For his pre-walk-through walk-throughs in 2008, he enlisted Baltimore firefighters to play scout-team defense.

“If those guys messed up, he’d get on their [butts], too,” said Willie Anderson, a former Baltimore Ravens offensive lineman and current skills trainer. He laughed. “He’s a smart man and a good teacher, and everything’s life-or-death. If you use the wrong foot on a [protection scheme] in walk-through, it’s life-or-death.”

On Zoom, perhaps sensing the players’ surprise at the old footage, Matsko pointed out one player’s feet and another’s hands. Linemen get bigger, he said, but the mechanics of moving defenders stay the same. Now, this technician’s mind-set is crucial for Washington, with a line young and in flux, and it illuminates a job often overlooked by those outside the NFL. If offensive line is among the most anonymous positions in sports, its coaches are even more so.

But many experts, including ESPN analyst Louis Riddick and former quarterback Sage Rosenfels, say a head coach’s most important positional assistant is the offensive line coach. They say this because he must handle volume (nearly half the offense), proximity (five players moving as one) and cohesion (blocking requires a difficult blend of chemistry, communication and spatial awareness). They say this because many head coaches see the line as a tone-setter.

Coach Ron Rivera said he thinks offensive line coach is “right up there” in importance with quarterbacks and defensive line coaches. When the Carolina Panthers hired Rivera in 2011, he hired Matsko, and the two have been together since. The Panthers regularly fielded strong running games during Rivera’s tenure, and Matsko was credited with helping develop Andrew Norwell from an undrafted free agent into one of the NFL’s best guards.

This weekend, when Washington faces its previous line coach — the Cleveland Browns’ Bill Callahan, who is seen as one of the league’s best — watch for more than just the linemen. Look at how the teams run the ball. Many line coaches, including Matsko and Callahan, help design the preliminary ground game while the offensive coordinator looks at passing.

“Then we work together just kind of blending them together,” Washington coordinator Scott Turner said. “[Matsko also] does a great job with our protections and everything like that.”

Brandon Thorn, an offensive line analyst, pointed to systemic factors increasing the value of offensive line coaches. The talent base at the position is smaller because most big kids want to play defensive line; there’s a dearth of skilled coaches even at the college level; despite the NFL’s recent embrace of spread-offense concepts, most college schemes still don’t properly prepare linemen for the pros; and the past few collective bargaining agreements have reduced contact practices. Perceived decline in the quality of O-line play has fueled the rise of independent trainers, such as Duke Manyweather and LeCharles Bentley.

Geoff Schwartz, a former guard and current analyst, says having fewer padded practices hurts the most. It affects linemen more than any position except maybe quarterback, he said, because the line is “a reps-based position” more reliant on skill than talent.

“I can do a pass set on air, but that’s 5 or 10 percent of the actual job that I’m doing on Sundays,” he added. “I got to be able to do that with someone running full speed at me and make contact and have good power and good balance. … [The lack of reps is] going to continue to be an issue for offensive linemen, especially in our development.”

In Washington, Matsko’s importance is heightened still. He’s the most veteran coach on a new staff building up a young offense. He’s navigating an inexperienced left side and the absence for the next few weeks of Pro Bowl guard Brandon Scherff, the unit’s best player who sprained the medial collateral ligament in his knee in Sunday’s loss to the Arizona Cardinals.

It’s hard to know how Matsko thinks it’s going — he declined an interview request — but it’s likely he will meet growing pains with fervor. The best illustration of Matsko’s tenacity is what he told the Los Angeles Times in 1989 following a Southern California loss to Illinois: “I would have liked to have played Illinois again that night in the parking lot,” he said.

In previous interviews, Matsko has said he “won’t tolerate a lack of effort or disrespect, and I will not disrespect the players.” Even though Matsko changed much of his new linemen’s technique — new steps, new angles, new footwork, new terminology — he didn’t reinvent them. Right tackle Morgan Moses praised Matsko for telling the Callahan holdovers, “There are some things that I’m not expecting you guys to change, because you’ve been coached well.”

This summer, Matsko also emphasized aggression. Former tackle Paul Adams remembered the coach telling the linemen they needed to be conscious of it, underscoring the point by sending them a golf article debunking “muscle memory.” Matsko wanted them to think every day about blocking their guy into the dirt. This was all to recapture the mind-set of the unit’s glory days, when the franchise won Super Bowls behind “The Hogs.”

“They kind of want to get that identity back,” Adams said. “It’s, ‘We don’t match the defensive line’s intensity; they match ours.’ ”

Anderson, the former lineman, said mental toughness was a focus for Matsko. Those who didn’t come from hard coaching sometimes struggled to play for him, and those who did earned his respect. In 2008, the Ravens lost a brutal, physical game to the Pittsburgh Steelers. Anderson dreaded the locker room because the linemen had missed “a bunch” of assignments. But Anderson remembered Matsko telling them he was “damn proud” because, while they had made mistakes, they had played hard and totaled more than 30 “de-cleaters” — Matsko’s nickname for pancakes or dominant blocks.

This summer, Anderson again worked with Matsko while training Saahdiq Charles, the left tackle Washington drafted in the fourth round. After the draft, Matsko told Anderson to teach Charles how to expand the pocket by pushing defensive ends. He didn’t want defensive ends riding the block to the top of the pocket, which Anderson calls “tetherball technique.” Anderson understood because, when he played right tackle for Matsko in Baltimore, he protected a rookie named Joe Flacco.

If Flacco struggled to find an open receiver, he often stayed at his original drop (nine yards) rather than climbing up in the pocket. This left him vulnerable to tetherballing defensive linemen. Anderson says Matsko foresaw a potentially similar situation with second-year quarterback Dwayne Haskins.

This is Matsko, operating behind the scenes, letting his work speak. Sunday in Arizona, Matsko appeared on the field about two hours before kickoff with swing tackle David Sharpe. They were two of the only people out there, specks in an empty stadium, and Matsko began to drill Sharpe on his footwork.

Down near the Washington end zone, Sharpe exploded out of his stance with choppy steps left. He seemed to want his left foot, which started on a yellow line, to end up on a black line about a yard away. Sharpe set again and again, with Matsko interjecting to correct an angle or shuffle width. Sharpe never made it into the game Sunday — he hasn’t played a snap all season — but Matsko kept watching, his arms crossed, his mouth a thin line. When Sharpe was done shuffling left, he turned around to go right.

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