Mitch Morse has six months of snaps to his credit, and this morning, he has to be happy for each and every one of them. The rain has just picked up at Missouri Western State, the longtime training camp home of the Kansas City Chiefs, and along with a 300-pound nose tackle inches from his face, Morse now has to deal with a slick football between his taped-up fingers. As Alex Smith barks the cadence, Morse fires the ball up into his quarterback’s hands. He pauses briefly before ambling downfield to set up a screen pass for Jamaal Charles. The snap is fine. The pass is complete. A hypothetical disaster is averted.

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All of our NFL preview coverage! A rookie from nearby Mizzou, Morse was a member of the Chiefs’ starting offensive line for Kansas City’s first preseason game, but the most important move he’ll make in his transition to the pro game isn’t the two hours on I-70. It’s two spots down the offensive line. For the past two seasons, Morse was the starting right tackle for a team that played in the SEC championship game, but from the moment he got to K.C., his place has been at center. Morse was at the NFL combine when he first heard that teams were looking at him to play center. That’s when he went to work on the snaps. “It was a challenge, but I was ready for it,” Morse says. “I knew I was going to fall a few times before I could stand.”

Morse’s shift is just the latest in a recent series of outside-in moves for early-round picks on teams gunning for the playoffs. Zack Martin started at left tackle for four years at Notre Dame, but last year, the 16th overall pick was an All-Pro guard for the Cowboys. Joel Bitonio didn’t quite reach those heights for the Browns, but he was stellar in his first season at left guard after manning the blind side during his time at Nevada. And after undergoing offseason back surgery, Ravens left guard and former Iowa State tackle Kelechi Osemele was among the most dominant linemen in football at points last season.

The migration inward hasn’t slowed this year. After a few months dabbling at right tackle, sixth overall pick and part-human, part-monster-truck Brandon Scherff seems to have settled as a right guard for Washington. And fellow college tackles La’el Collins (Cowboys) and Jamon Brown (Rams) are in the mix to start at guard as rookies.

In the past, bumping inside was seen as a demotion, at best, and as an indictment, at worst. Inside positions were the Island of Misfit Tackles, where players who were too small, or too short-armed, or too slow-footed had a chance to survive, safe from the predators tearing off the edge. As defenses shift further from tradition, that hierarchy has started to blur. The requisite skills needed are unique inside and out, and as more tackles switch to guard and center, they’re realizing that more distance from the ball doesn’t mean more prestige.

“People just think it’s easy,” says T.J. Lang, the Packers’ right guard and a former college tackle. “You hear it all the time on the big networks, they’re doing their scouting reports and saying, ‘Well, this guy can’t play tackle, so he’s going to be a guard.’ They say that like it’s a slap in the face. They act like it’s where tackles go if they can’t make it outside. I’ve never bought that. Tackles switch to guard for a lot of reasons, and it isn’t always easy.”

Frustration is emanating from LeCharles Bentley’s voice. Before starting his answer, a deep sigh comes through the phone. “It gets so annoying to hear how the powers that be diminish the value of the skill set required to play guard,” says the former NFL center turned offensive line guru. “‘You can’t play tackle, so you can play guard.’ That’s a complete fallacy.”

Physical profile is the first way many scouts separate offensive linemen by position. It didn’t take long for Chiefs offensive line coach Andy Heck to realize Morse wouldn’t be playing tackle in the NFL. “The first frame of film I saw, just by body type alone,” Heck explains. Some players simply can’t escape the fate their bodies have all but guaranteed. Morse’s 32¼-inch arms put him in the fourth percentile among tackles, which would make dealing with the likes of Robert Quinn and Von Miller problematic. But what makes him an ideal candidate for a move inside isn’t just that he can’t play tackle. The traits he does have are the prototype for an excellent interior lineman.

“As you continue to watch,” Heck says, “you see he has the explosion, the leverage, the speed and quickness you’d want in an inside guy.”

On the inside, where space is scarce, leverage comes at a premium. That’s why shorter players can be considered an ideal fit; playing lower to the ground means better movement off the ball. But it isn’t always that simple. “There are 6-foot-2, 6-foot-3 guys who play high as kites,” Bentley says. That thought works the other way, as well. Alex Boone, a client of Bentley’s who was long considered a classic left tackle, stands 6-8 but is flexible enough that he was able to settle in at guard for the 49ers. Bentley says the basic habits that make successful offensive linemen are transferrable across positions. The nuances are what separate guard from tackle, and many of those are learned skills.

During his first two years in the league, Lang worked as a backup all along the line in Green Bay, but before his third season, he knew it was time to home in on a single spot. The Packers had a hole at left guard, and Lang spent his time during the 2011 lockout learning what that position was designed to do in Green Bay’s offense. He started the only place he could — from the ground up.

“The biggest thing for me was getting into a comfortable stance. At tackle, you see guys that are out here,” Lang says, with his feet noticeably staggered. “Guard, you’re pretty even. That took me a while to get used to. When you’re going into the game and you’re not even comfortable in your stance, you have a million thoughts going through your head.” After figuring out how his feet should start, Lang shifted his focus to where they should go.

A pass set for an offensive tackle is meant to create the width of the pocket, as Lang explains it. The movement is made at an angle, somewhere between a movement directly away from the ball and a step backward into the backfield. It’s typically a series of steps, made without the fear of a bull rush, coming together in the split second after the ball is snapped.

At guard, space and time disappear. What Lang had to learn was how to shorten that process to a single step, with his hands coming up at the very moment his foot hit the ground. Going from tackle to guard means battling B.J. Raji–size linemen instead of linebackers built like Clay Matthews. Lang, Bitonio, and others bring up how often their hands lagged early on. The need to establish control inside is instantaneous. Any delay, and the play is already over. “The punch has to be so much quicker,” Bitonio says. “It’s a hand battle right away. At tackle, you might take three steps and then you might have to engage a guy. I was basically having to relearn how to use my feet and hands.” More crucial than anything, though, is maintaining the precious few inches between a guard’s heels and the prized possession setting up to throw.

“[At guard] you’re responsible for the depth of the pocket,” Lang says. “You don’t have room to get pushed back.” Bitonio paints a slightly less comfortable picture. “At guard, it just happens so fast,” he says. “Bang, bang. If you get too much room off the ball, you’re sitting in the quarterback’s lap.”

Five days before the first playoff game of his career, Kelechi Osemele got some news from Andy Moeller, then the offensive line coach for the Baltimore Ravens. After Osemele started all 16 games of the season at right tackle, Moeller was moving the rookie to guard for the wild-card game against the Colts. Osemele had long known the move might happen. At Iowa State, he was among the strongest players on the roster, a devastating mauler in the run game whose singular talent couldn’t be maximized at left tackle. “He’s such a physically dominating player,” says Matt Birk, the Ravens’ center at the time. “You don’t see that many guys inside who can physically dominate people, and he can. That’s huge. In today’s NFL, it’s so often a stalemate. He can move people off the ball by himself.”

Bryant McKinnie showing up out of shape was all that kept Osemele from initially playing guard, but with McKinnie ready to play tackle, Osemele was free to take his natural spot on the line. With their most talented five players finally on the field, the Ravens’ line finally coalesced — the result was a Lombardi Trophy.

Moving to guard also provided the opportunity for Osemele to embrace the aggression that defined his game. “That’s why you start playing football,” Osemele says. Even if he’d never played the position, he’d always been a guard. Lang is wired the same way. “I didn’t really have that mind-set to be a tackle where I had to be patient,” Lang says. “I wanted to get on guys now, and sometimes that got me in trouble. Guard was definitely more comfortable.”

Like the physical requisites, there’s a specific set of mental attributes that separate whether players are suited to play inside or out. Joe Thomas, the best left tackle in football, has famously short arms, but no lineman alive is calmer and more unflappable when pass blocking. “The key to playing on the outside is understanding angles,” Bentley says. “It has nothing to do with how tall you are. It has nothing to do with how long your arms are. Does that help? Yeah, it can help, but that’s not the no. 1 requirement.” Kelvin Beachum, who stands a relatively paltry 6-2 and manages to play left tackle for the Pittsburgh Steelers, gets by the same way.

When Birk, a taller-than-average center who played tackle at Harvard, made the move inside during his rookie year, his interior education came courtesy of Jerry Ball. By 1998, Birk’s rookie season, Ball was 34 and seven seasons removed from the most recent of his three Pro Bowls, but still, dealing with the 330-pound nose tackle was a daily chore.

Ball would torment the rookie, inching farther inside before the snap, baiting Birk into thinking he meant to crash hard across the center, only to dart back toward his original gap as the ball was snapped. “He really made me realize it’s about more than just power,” Birk says. “There’s a lot of thinking that goes on in there.”

Osemele had similar lessons, courtesy of Haloti Ngata. Learning to deal with Ngata came in waves during Osemele’s rookie season. The physical challenge came first, slowly figuring out how to anchor down and hold up against all 340 pounds of superstar talent. When the bull rush ceased to be enough, Ngata started peppering Osemele with an inside swim move he just couldn’t solve. “That was really hard to stop,” Osemele says. “Being able to transition from anchoring and then mirroring after that, I learned from blocking Haloti Ngata every day.” It wasn’t until the third day of practices before the playoffs that Osemele finally solved the riddle. “I remember the first time that I beat him at one-on-ones, Marshal [Yanda] told me, ‘If you can beat that guy consistently, the game is gonna pretty much be easy.’” Many of them have been since.

The highest level of interior lineman aptitude is typically reserved for centers. In some schemes, centers are required to be a bit quicker than guards — that’s true for Morse and the Chiefs — but in most, it’s the center who’s responsible for making each of the calls. “You always want to identify the guys that [you think] ‘OK, he could be a center, now let’s see if he has the aptitude mentally to handle that,’” Heck says. A Harvard graduate who scored a 46 on the Wonderlic, Birk had no problem with that side of the game — and Morse appears to be cut from the same stone. The closer a lineman gets to the ball, the more moving parts he has to understand, and that’s a responsibility Morse is still learning. “Just identifying defenses, figuring out how different plays run into different defenses,” he says has been his most significant challenge so far. “Everything has rules, and you have to learn each of those rules.”

Teams that met with Zack Martin before last year’s draft were split on his NFL future. Some saw him as a tackle, some as a guard, and some as either. Then-Dallas offensive line coach Bill Callahan was more certain. The Cowboys viewed him as a guard from the start. “I didn’t take a rep anywhere else,” Martin says. “I didn’t have to worry about playing left guard or right tackle.” Bitonio was given the same treatment in Cleveland, where then offensive coordinator Kyle Shanahan wanted him to focus on little else but becoming the best left guard possible.

The goal is habit creation and muscle memory. These days, Birk talks like a man who recently retired from football. He tosses around plenty of golf references, and learning to play inside, he says, is like a golf swing. There are dozens of tiny movements, each of which is capable of throwing off the complete motion when improperly executed. But at the highest level, they come together without having to consider a single one individually. “I’ve got to snap that ball, get my head and my hands across, and step all in a single second,” Morse says. It’s mastery through thousands of repetitions, and it goes far beyond simply shifting one spot down the line.

Bentley even goes a step further. With nowhere to hide, a tackle’s mistake is more visible, but the magnitude of a mistake for an interior lineman is actually more significant. Because the action happens so fast, any misstep means there’s almost no opportunity to recover. Each of these guards, without prompting, used the word “tighten” when describing how their footwork had to change. Movement on the inside is too valuable to waste. “You have to take really calculated steps,” Morse says. “Not that you don’t have to at tackle, but these are just so much more compact.”

That premium on polished play may be part of teams’ thinking with players like Martin, Bitonio, and now Scherff. Left tackle is still the prestige position on any line, but those days are dwindling. Of the five highest-paid defensive players in football, three are primarily interior defensive linemen, and the only edge rusher in the group — Justin Houston — spends most of his time coming off the right side of the offensive line.

The era of linemen clamoring to be the left tackle, to man the island to the outside, may be coming to an end. There was a time when Joel Bitonio might have scoffed at the idea of playing guard, but not anymore. “In college, it was like, ‘Guard? What the hell is that?’” Bitonio says. “Now, I don’t even remember that I played left tackle.”