The identity of Chip Kelly’s offense is not the finesse, east-west approach that many perceive it to be. Rather, it all starts with the inside zone — a physical, downhill run play that aims to knock the crap out of defenders and push them backward with double teams. It’s a play that Kelly’s offensive line in Philadelphia spent over 40 percent of their practice time perfecting, according to Eagles offensive tackle Lane Johnson.

But when you run the inside zone as often as Kelly’s teams do, defenses will begin to tighten up and look to clog the middle. At that point, the offense must be able to threaten the perimeter and shift the defense’s focus away from the interior so that they can later return to their bread-and-butter. Kelly accomplishes this with his two base outside runs: outside zone and sweep.

Outside Zone

"If we feel [the defenders begin to tighten their techniques] or we start to get twists and blitzes on the inside, we run the outside zone play," Kelly said at a coaches clinic in 2009.

The great thing about the outside zone from the offensive line’s perspective is the rules for determining who blocks who from the inside zone — identifying the point defender, cover or uncovered, creating appropriate double teams, having the quarterback read the extra defender in the box, etc. — remain intact. As Kelly puts it, "the who we block is the same, but the how we block is the difference on the outside zone."

Whereas the inside zone is about creating vertical movement, the outside zone is all about moving laterally to outflank the defense and pin them inside. To accomplish this, Kelly’s teams use a technique he calls the "rip and run."

Offensive lineman begin the play by stepping laterally to the play side (possibly even backward if they are on the backside of the play), and attempting to reach the outside shoulder of their designated defender. If the lineman is successful in getting to the outside shoulder, he pins the defender inside (rip). If the lineman has not reached the defender by the third step, he switches gears and looks to run the defender all the way to the sideline (run).

When executed successfully, there are two basic outcomes for the offense. A successful rip on the play side piles up everything behind that block and seals off the backside, allowing the ballcarrier to get outside and up the sideline. If the rip cannot be had and the offensive line has to run the defense to the sideline, the running back will stick his foot in the ground and cut straight up the field.

During Kelly’s time in Oregon, you could also differentiate the outside zone from the inside zone by the alignment and path of the running back. The exact alignment would change based on the specific ballcarrier and how quickly he would hit the hole, but running backs would generally be tighter to the quarterback and further from the line of scrimmage on inside zone, and then would align wider and closer to the line of scrimmage on outside zone.

Once he got to Philadelphia, however, Kelly made the alignment of his backs more homogeneous to better disguise his intentions, as you can see from the above image. And as Kelly touched on during his clinic talk, adjusting the back’s alignment for different run plays is less of an issue than it seems on the surface. "If the defense is looking at the depth of the backs and trying to figure out what play is coming, they are thinking about the wrong thing," Kelly said. "If that is the key, [they] will be fooled."

This is largely because Kelly has several variants on his base run plays to take advantage of defenses if they begin to overplay one side of the formation based on the running back’s alignment (think of the way inside zone and power look nearly identical to start but hit different sides of the line), which I’ll be covering more in-depth in my next article.

Sweep

Vince Lombardi’s power sweep is perhaps the most famous play in football. While the old-school Lombardi sweep hasn’t been run on a regular basis in the NFL since the Walsh-era 49ers — at least in its original split-backs variant — Kelly’s sweep is effectively a modern take on the classic play.

Much like the power play, the sweep utilizes man, or gap, blocking from the offensive line as opposed to the zone-blocking scheme used in Kelly’s other base runs (inside zone and outside zone). Down blocks on the play side attempt to seal the defense inside and wall off pursuit from backside defenders while a pair of lineman pull around the edge to create an alley for the ballcarrier.

In Lombardi’s version of the sweep, the guards served as the pulling lineman. Kelly, on the other hand, switched up his pullers with the Eagles, most often utilizing a center/guard combination to take advantage of the Eagles’ athletic center, Jason Kelce.

When everything goes according to plan, you’d be hard pressed to find a prettier play to watch than the sweep.

From the Eagles film I watched, it appeared that the sweep actually began to take over for the outside zone as Kelly’s preferred perimeter run play. Considering the success Philadelphia had with the play, it was easy to see why.

♦♦♦

It’s no coincidence that Chip Kelly’s base run game — inside zone, outside zone, power, and sweep — features a heavy amount of crossover in style and teaching points. As Lombardi did, Kelly believes that it’s more important to do a few things well than a bunch of things poorly. By utilizing a small number of runs that feature many of the exact same blocks, Kelly is able to minimize the amount of material his offensive line needs to learn while still providing them with all of the answers they will need to handle whatever the defense throws at them.

Combined with the high number of reps players receive during practice, Kelly’s system allows his offensive line to spend less time thinking and more time reacting, a key to performing nearly any task at a high level. As Kelly said during his clinic talk, "If you can keep it simple for your players in the offensive line so they have confidence going into a game, you have an opportunity to win the game."