Before the snap, his mind rummages through a mental checklist.
Josh Sitton studies the defensive linemen's body language, just like a poker player reads his table. He checks their stance. He's aware of weight distribution, hand placement, alignment. Information collects rapidly, often leading to the same outcome.
Before a play begins, Sitton usually knows what's going to happen.
"It's weird. You almost see what they're going to do before they do it," Sitton said. "… I just kind of take a mental picture and feel like I'm able to know what they're going to do."
Sitton wears a rugged look. With long hair and a bushy beard, his appearance fits seamlessly on the offensive line. Don't let the guise fool you.
The seventh-year guard has one of the brightest minds inside the Green Bay Packers' locker room, right up there with quarterback Aaron Rodgers.
"He's obviously got the elite talent," rookie center Corey Linsley said, "but not everybody with the elite talent plays like Josh. There's a reason for that."
Sitton, along with right guard T.J. Lang, leads a group that has protected Rodgers almost flawlessly over the past month. The Packers' offensive line has allowed two sacks in four games since the bye week, according to Pro Football Focus. Both came last week against the New England Patriots.
The 6-foot-4, 320-pound left guard has a lot to do with the success. Sitton, a second team All-Pro last year, is the one offensive lineman who has been with the team every season since Rodgers became the starting quarterback in 2008.
He's only getting better.
Through 12 games, Sitton is piecing together one of the best seasons among offensive linemen in the league. He hasn't allowed a sack since Green Bay's loss to the Cincinnati Bengals on Sept. 22, 2013. His stretch of 26 games without a sack is the longest active streak in the NFL, according to Pro Football Focus.
This season, only seven other guards have allowed no sacks while playing at least 50 percent of snaps. With five total pressures, Sitton is tied with Baltimore Ravens guard Kelechi Osemele and New York Jets center Nick Mangold for the NFL lead.
What separates the three? Sitton is the only one in the group who hasn't allowed a sack.
"He's the best guard in football," defensive end Mike Daniels said. "He's been the best guard in football, from what I've seen, since I've been here. To be able to practice against him, I can say that's definitely helped elevate my game."
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Nobody inside the Packers' locker room disputes Sitton's stature in the league. He is a Pro Bowler at the very least, defensive tackle Letroy Guion said. Defensive end Datone Jones simply called Sitton "special."
But what, specifically, puts Sitton in the conversation for best guards in the NFL?
"He's huge, first of all," Daniels said. "Then he's got that beard and all that hair, so he's pretty intimidating. You don't see that often. He's very strong. Deceptively strong, actually. You may look at him and say, 'OK, he's a big guy.' But when he gets his hands on you, he doesn't let go.
"I've seen D-tackles run into him and just stop like they hit a wall. That's what he is. He's like a giant, brick wall."
No doubt, Sitton's physical tools are tailor made to play guard. He is 6-foot-4, 320 pounds, an ideal frame for the position. Linsley raves about Sitton's quick feet and broad shoulders. Physically, Linsley said, Sitton is the "complete package."
Linsley believes it's Sitton's mind that makes him elite.
"I've always been a guy that just understands the game extremely well," Sitton said. "Football has always come very naturally to me, the mental part of it. I think it's always given me a little bit more of an advantage than most. If you can have the mental part down, it makes the rest a lot easier."
Linsley has directly benefited from his teammate's football IQ.
The rookie goes back to his first game. When the Packers visited the defending Super Bowl champion Seattle Seahawks in September, Linsley immediately impressed in his debut. His performance was imperfect.
One play, in particular, sticks out three months later. Linsley wouldn't go into specifics — careful not to reveal part of the game plan — but there was miscommunication at the line of scrimmage. Only, Linsley didn't know he had the wrong call.
Sitton studies more than the defensive linemen across him, so the veteran recognized the rookie's confusion. Subtly, he compensated on the snap, "laying heavier" into the player Linsley was supposed to block so the rookie wouldn't get beat. The Packers avoided a negative play, moved on with their drive.
It wasn't until weeks later that Sitton finally told Linsley what happened.
"I was like 'Damn, he knew all that?'" Linsley said. "He knew what was going on in my mind and what I was going to do, so he reacted accordingly. That's, like, the tip of the iceberg of his knowledge of the game. We'll be sitting at meetings, and he'll notice something wrong with a route in one of the slides. He's like, 'Hey, shouldn't that be that?' Coach is like, 'Oh yeah, good catch Josh.'
"That's amazing. I think that's the most untalked about thing with Josh."
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There's another trait required to play along the offensive line, something embedded from the beginning. In the trenches, toughness is proven every snap. Defensive tackle Josh Boyd believes that grit is what separates Sitton from the rest.
These past four games, Sitton has played with a torn ligament in his left big toe. It's similar to an injury that ended San Francisco 49ers linebacker Patrick Willis' season in mid-November. If Sitton didn't play on the offensive line — where a quick burst of raw speed is unnecessary — he said the injury likely would've warranted surgery.
Yes, his big toe hurts — and that's putting it mildly. Sitton hasn't complained once, determined to push through the pain.
"I think he just has that tenacity, that toughness that he won't get beat," Boyd said. "You're going to have to beat him to show him. Because everyone is good in this league, it's something that sets you apart from other guys. I think that's what it is."
Four games on a bad toe. Yet, the sackless streak continues.
This is where Sitton's mind is especially valuable. Physically limited, Sitton compensates by anticipating what's about to unfold on the field. If defensive linemen don't make their pass-rushing stance and run defense stance look identical, Boyd said Sitton will know the difference.
It takes more than football smarts to succeed as an NFL guard, but raw talent doesn't necessarily make a great player. There is a perfect mixture, blending the mental and physical aspects of football. It's a level Sitton has reached in his seventh season.
"Obviously, it's a necessity with the physicality," Linsley said. "The smarter you can play, the more you can use your physicality to work appropriately. Because it really doesn't matter if you're the toughest guy in the world. If you're blocking the wrong guy, your guy is still going to make the tackle. It goes hand in hand. It's just as important."