[Editor's note: This is the first installment in Senior Analyst Mike Renner's“Teaching Tape” article series, which takes a look at the best positional units across the NFL.]

It’s early in the first quarter of the Cowboys' Week 3 matchup against the Falcons—the first game of many without Tony Romo starting under center. Atlanta came in knowing Dallas wouldn’t be able to win the game through the air, but so far it hasn’t mattered. Running back Joseph Randle broke off runs of 28 yards and 37 yards on the Cowboys' three-play scoring drive to start the game, both coming against eight-man boxes. With 11:09 remaining in the first, Randle receives his third handoff, and the gamebook reads the following:

Unfortunately, not a single name is mentioned besides Randle’s, who had the easiest job on the entire play—run in a straight line. What the gamebook doesn’t tell you is that every block on the front side of the play was executed to absolute perfection.

This is the Cowboys' offensive line. It's a unit that blocked for castoff running backs and quarterbacks the majority of last season, yet still came away as PFF’s highest-graded pass-blocking and run-blocking line. Unlike some recent top offensive lines—like the 2012 San Francisco 49ers and the 2013 Philadelphia Eagles—the Cowboys aren’t doing it with anything innovative or different. They simply execute far better than any other team in the league.

It starts with not having any weaknesses along the offensive line. La’el Collins was their lowest-graded starter, and he still ranked only 43rd out of 66 starting guards last season. They combine that high floor with freakish top-tier talent. Everyone knows about left tackle Tyron Smith’s dominance. Our highest-graded tackle last season, he can move like a tight end. Watch Smith chase down a 3-technique here on the backside of the play and bring him to his knees.

Then you have center Travis Frederick, the second-highest-graded player at his position this past season after being the highest-graded the year before. He’s probably the quickest center off the snap of the ball and definitely the best reach-blocking center in the NFL. A poor block from the center can blow up a run quicker than any other position, and Dallas doesn’t need to worry about that with Frederick in the middle.

With no weak links in pass protection, they’re a well-oiled machine. No one embodies that more than right guard Zack Martin. He was a left tackle at Notre Dame, and there’s no reason that, with his abilities, he couldn't be the Cowboys' right tackle of the future once Doug Free retires. If Green Bay's Josh Sitton is “1a” for pass-protecting guards in the NFL, then Martin is “1b.” In 1,010 pass-blocking snaps his first two seasons, Martin only gave up 27 pressures. How often do you see a six-man pressure (and a linebacker-defensive tackle stunt) picked up so flawlessly?

Their effectiveness as a whole comes from keeping it simple. Let’s start with the outside zone run, one that every single team in the NFL has in their playbook. This is the Cowboys' bread-and-butter play, one that they ran on 47.7 percent of their handoffs a year ago—the fifth-highest rate in the NFL. The beauty of the run is that any single dominant block from an offensive lineman can result in a big run.

If you could boil down the goal of offensive linemen on outside zone runs to one word, it would be control. The line isn’t trying to take defenders off the ball (although that’s a plus) as much as they are trying to overtake gaps, create horizontal space, and make sure defenders can’t separate laterally to finish tackles. The responsibilities will differ playside (where ideally they create width) to backside (where ideally they cut off), but both ultimately want to “lock in” on their respective defenders. It puts a ton of stress on the defense, because they have to maintain gap control while sprinting sideways. If a defender gets reached or cut out of his respective gap, and the running back is able to find it, then there will be a crease to the second level.

The key, though, is the running back reading it correctly and concisely. Any hesitation or delay in the backfield can spell disaster for the play. Once a decision is made by the running back, he needs to make one cut and get upfield. On the play below, the initial read is the edge man on the line of scrimmage. The left tackle/guard combo wants to make that a quick read and take the defender fully whichever way they can. Since the defensive end dives inside to take the B-gap, the left guard, Ronald Leary, continues to take him inside. Leary seals the end all the way into the A-gap, meaning the defense has lost gap control. Because of that, and a perfectly-executed lead block from fullback Tyler Clutts, Darren McFadden has acres of green grass to work with. What the running game was missing from the year before was the guy who could make DeAngelo Hall miss there and turn it into a huge gain.

The interesting dichotomy of the Cowboys' running scheme is that their second-most-utilized run concept is nothing like outside zone. It’s also the simplest of run plays: the blast. It’s characterized by hard, straightforward double teams on the interior players, with single blocking on the edge. The offensive linemen on the double-teams each eye a linebacker, and if they do start coming downhill, the lineman peels off to seal. It’s far from a home-run threat. Only three of their 60 attempts went for 10-plus yards, but at the same time, it’s also a consistent line-of-scrimmage mover, with only two such plays going for negative yardage.

The goal of the play is simple: walk the defensive tackles backward into the linebackers. That essentially puts the linebackers on an island where they can’t commit to a gap. The one thing it does have in common with outside zone, though, is there is no set path for the running back. He’ll have to read where the blocking wins and where the linebackers fill, and then chose the ideal gap.

As you can see in the above run, the running back can make a well-blocked play look worse than it is. McFadden cuts completely across the leverage of Smith and Frederick, even though every lineman is locked in on their blocks.

The more I reviewed the Cowboys' 2015 performance, the more I understood why they were willing to eschew conventional wisdom by taking a running back—Ohio State's Ezekiel Elliott—in the top five of the draft. They gave their backs a clean run to the safety-level far too often to only average 4.7 yards per carry as a team. Getting a running back who combines vision with elusiveness and power will be a huge boon for the Cowboys' offense. The scary thing is that, with four starters at 25 years of age or younger, the unit could realistically be even better in 2016.