At the center of Atlanta’s stellar first half of the season has been ... the center. Alex Mack has elevated the play of his linemates, a big reason why the Falcons are soaring at midseason.

This story appears in the Nov. 14, 2016 issue of Sports Illustrated. Subscribe to the magazine here.

To explain how center Alex Mack has become a crucial figure in the juggernaut that is the 2016 Falcons’ offense, you have to start with something surprising—something that isn’t exactly typical among the league’s top offensive line iceboxes. You have to start with ... running.

In 2009, after Cleveland had made Mack the 21st pick in the NFL draft, out of Cal, teammate Joe Thomas was perplexed by Mack’s behavior during one of the team's first off-season practices. Mack’s arrival had coincided with the hiring of coach Eric Mangini, who, like his mentor, the Patriots’ Bill Belichick, made players run laps if they made simple mistakes—jumping offside, for example, or, in Mack’s case, executing a poor snap. Usually, a player would run approximately 400 yards at an even trot—especially if the offender was a bulky lineman.

“Not Alex,” says Thomas. “The way he ran laps, it was like he was Michael Johnson in the Olympic final. He had to be running, like, 50-second 400s—and he ran a lot of them because he had a lot of bad snaps and a lot of offside penalties as a rookie. But he would get going, and he would only miss one play, which was just amazing. The way he’d run, with his arms flailing, his head back, bouncing side to side—it was really a sight to behold. Alex does not have very good running technique, but he definitely runs really hard.”

Mack certainly made an impression on Thomas.

“I used to laugh to myself, thinking, Who is this goofball? Just take your time,” Thomas says. “But he was determined to get that lap over with as quickly as he could. He didn’t want to miss any more time learning the position. He’s such a master of his craft.”

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Seven years later, at 30, the NFL’s Running Man hasn’t slowed down. Mack (who opted out of his Browns contract last March) was one of Atlanta coach Dan Quinn’s top targets in the off-season. The three-time Pro Bowler arrived last summer at training camp in Flowery Branch, Ga., with its brutal blend of heat, humidity and unrelenting sun, and kept his foot on the gas. “He had a number of screen plays in practice, rep after rep, and he’s hauling ass about 45 yards down the field trying to get a block in front of [running back Devonta] Freeman,” says Quinn. “Little interactions like that reaffirmed what he’s about as a competitor. You could feel his strain and effort.”

“Offensive linemen just don’t do that,” says right tackle Ryan Schraeder. “And when he does that every play? It makes me feel like I have to do that every play. Before I know it, I’m running downfield, trying to pick guys off. Stuff like that rubs off.”

“Our receivers see that, our running backs see it, I see it,” says quarterback Matt Ryan, a nine-year veteran. “The more guys you have doing that, the better off you’re going to be.”

It’s not just his hustle that is rubbing off on his teammates. Left tackle Jake Matthews is the son of Hall of Fame guard Bruce Matthews and the nephew of retired linebacker Clay Matthews Jr., so not much surprises the third-year pro. But observing Mack in his first positional meeting with the Falcons caused Matthews to alter what even he expected of himself. “You think: He’s an older guy, probably gets it all, has all the answers,” says Matthews. “But it wasn’t that way. He was firing questions nonstop. And I think it’s influencing the line a lot. He wants to pinpoint every little thing that can possibly happen and make sure we’re prepared for it. That’s been really refreshing and has helped a lot of the linemen grow and think about things in a different way. I’m trying to follow his lead because I want to get where he is.”

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Mack got where he is a long time ago—he has been an excellent player for years. Before the 2014 season Cleveland placed the transition tag on him, allowing the market to determine his compensation. The Jaguars offered him a five-year, $42 million contract, and the Browns exercised their right and matched the offer. Through the first five games of 2014, with Mack in the middle and a trio of no-name running backs behind him, Cleveland averaged 26.8 points and 146.4 rushing yards per game. But in the second quarter of a 31–10 dismantling of the rival Steelers in Week 6, Mack fractured his left fibula and was lost for the rest of the season, breaking a streak of 5,279 straight snaps. The Browns averaged 15.0 points and 90.5 rushing yards per game the rest of the way. “That shows his value right there,” says Thomas. “Losing him really hurt.”

Coming back from injury and with his offensive coordinator in Cleveland, Kyle Shanahan, now relocated to Atlanta, Mack had a 2015 season that was good for most centers but not for him. In 2016 he's healthy and playing for Shanahan again. ProFootballFocus.com rates him as the No. 3 center this season.

Shanahan employs a run-based scheme similar to what his father, Mike, ran in Denver and Washington. The inside- and outside-zone running system is demanding for a center.

On an inside-zone run, Mack and a guard will usually double-team a defensive tackle and then scoot quickly to block a linebacker. Late in the first quarter of a 48–33 victory over the Panthers, Mack blasted standout defensive tackle Star Lotulelei with his right shoulder, directing him into the block of right guard Chris Chester. Mack then kept moving to hit All-Pro linebacker Luke Kuechly. Mack squared up Kuechly and turned to the right to form a wall that Freeman could run behind. Kuechly, the best middle linebacker in the game, was rendered helpless for one of the few times in his career, as Freeman scored from 13 yards out.

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The key block in Shanahan’s outside-zone runs is the reach block. When the move is not well executed, the result is often a tackle for a loss. There’s nothing misleading about the terminology: The block calls for the center to reach a player beyond arm’s length and control him, either by running him to the sideline or turning him back toward the play. Centers are usually at a size, strength and speed disadvantage against defensive tackles. It’s like a brown bear trying to take down a larger grizzly, and the brown bear has to snap a football first.

With 4:52 left in the second quarter in the Falcons’ 23–16 road upset of the defending champion Broncos, Mack had nosetackle Sylvester Williams off his left shoulder in the A gap between him and left guard Andy Levitre. Freeman was to go in the B gap to the left of Levitre. So for the play to work, Mack had to push Williams past the B gap, or somehow get his helmet between Williams and the B gap, and control him long enough for Freeman to get by. And Mack had no idea where Williams intended to go. It’s all reaction, and executing counter moves with feet and hands in two seconds.

Mack is one of the best reach blockers among centers, which is due to his wrestling background (at San Marcos High in Santa Barbara, Calif.), height (6' 4") and strong hands. “He has the size of a guard but the quickness of a center, and that’s pretty rare,” says Quinn.

Mack stayed low to get under Williams’s pads and gain leverage. He was then able to move his feet between Williams and Freeman. Williams didn’t allow himself to get turned, but Mack was able to control Williams enough that Freeman ran for a nine-yard gain.

Mack is stellar in pass protection too, and his experience allows him to recognize the schemes he sees and communicate them to his linemates. He’s had a calming effect on passing downs. Atlanta has gone from averaging 21.2 points per game in 2015 to 32.8 this season. Total yards have increased by 50.9 yards per game. The running game has gone from averaging 3.82 yards per attempt to 4.41, and yards per pass attempt has increased from 7.41 to 9.45, despite playing the second-toughest schedule (including back-to-back road games against stingy defenses in Denver and Seattle), according to FootballOutsiders.com.

“It’s hard to quantify the impact of an offensive lineman,” says Quinn. “It’s been deeper than the numbers for us. It’s been the communication at the line, leading the front in the run game. It’s been allowing the protections from him and Matt to be totally on the same page. He has a real standard in how he likes to play and how he likes to prepare. Honestly, he’s been a really good addition for us.”

Mack did not run away from Cleveland—even though the team was a combined 33–79 during his time with the Browns. “There was a sense of unfinished business,” says Mack. “I was drafted there, and I would have liked to have left the team better off than when I found it. I don’t regret any of my time there. I liked the coaches they brought in. Hue [Jackson] had a great attitude. It was more the fact that it was just another reset. It was frustrating to have another new coach, another new GM, and there was still the question of the quarterback. On the other hand, it was a great opportunity [in Atlanta]. Your career is only so long, and I was excited to get a fresh start.”

Mack’s contract with the Browns included an option for him to void the final three years of the deal and become a free agent, if he were willing to give up the $8 million he was guaranteed in ’16. Once owner Jimmy Haslam hired former Dodgers general manager Paul DePodesta (as chief strategy officer) and Sashi Brown (as executive vice president of football operations) in January, with their Moneyball approach, Mack’s departure seemed inevitable.

“The new analytics people didn’t really value the center position very much,” says Thomas. “They much more strongly value the outside players. They feel like building a team from the outside in is how you do it. You value your tackles to some level, but they really value receivers and cornerbacks and DBs. For Alex, I’m guessing it was, I’m the best player in the NFL at my position. Somebody’s going to pay me to be the best player in the NFL at my position. Why would I stay in Cleveland for somebody who doesn’t want me that much, for a team that doesn’t seem to be making progress? I want to go somewhere that’s got a quarterback, a lot of pieces in place, and maybe I can be the final piece of that puzzle.”

Atlanta did make Mack the highest paid player at his position in terms of guaranteed money ($28.5 million), giving him a five-year, $45 million deal on the first day of free agency. The Browns are rebuilding again, with a focus away from the ball, while the Falcons believe they have found the final piece of their puzzle.