Cowboys on the Chalkboard: One-Gap vs Two Gap Defense

Aug 16, 2014; Arlington, TX, USA; Dallas Cowboys defensive coordinator Rod Marinelli talks with the defensive line on the sidelines during the game against the Baltimore Ravens at AT&T Stadium. Mandatory Credit: Matthew Emmons-USA TODAY Sports
Aug 16, 2014; Arlington, TX, USA; Dallas Cowboys defensive coordinator Rod Marinelli talks with the defensive line on the sidelines during the game against the Baltimore Ravens at AT&T Stadium. Mandatory Credit: Matthew Emmons-USA TODAY Sports /

Cowboys on the Chalkboard will slow things down today and look at the trenches, explaining player positioning and one-gap vs two-gap.

The offseason is a great time to assess player performance and discuss upgrades and replacements. But before we can adequately grade and assess, we first need to have a grasp on what they’re being asked to do in the first place.

Not all defenses are created equal, and not all players are given the same opportunities to succeed – even if they play the same position. Gap responsibility is a big part of every front seven player (linemen and linebackers) and goes a long way in determining who the “playmakers” are and who the “grinders” are.

Before we dive right into the differences between the one-gap and two-gap defenses, let’s take a moment to first identify the gaps. A “Gap” is simply the running lane created by the positioning of the offense. They can be between two players, off the edge, and even created by a lead blocker and/or motion man. This brings us to our first chalkboard…

Cowboys on the Chalkboard – gaps /

Quite simply, this chalkboard illustrates the gaps in relation to the offensive linemen and tight ends. The gaps on both sides of the center are the “A Gap”. The gaps between the two guards and two tackles are the “B Gaps”. And the gap outside of the tackles are the “C Gaps”.

Add more tight ends to the line – add more gaps.

From there additional gaps can be created as the play develops. A fullback, H-back, or even receiver, could go in motion and act as a blocker setting up gaps on either side of them.

It’s a simple concept but it’s often taken for granted and that can be a mistake when trying to understand defensive schemes and individual responsibilities.

One-Gap vs Two-Gap Defense

The one-gap and two-gap defense refers to the defensive line’s responsibilities in the running game. Cowboys fans should be well accustomed to both since they have used both systems in recent years. Look below and you will see a familiar two-gap defense the Cowboys ran not-so-long-ago.

Two-Gap Defense (Offensive linemen represented with circles)

Cowboys 3-4 two Gap /

The linemen, as well as the linebackers, have two-gaps each with some obvious overlap between them. This ensures the defenses success and acts as an insurance policy should one player be neutralized and/or an offensive lead-blocker tips the scales and jumps into a gap splitting it into two.

Many 3-4 defenses, like the one the Cowboys ran under Bill Parcels, are two-gap systems like this.

They require defensive linemen (and many times linebackers) to be responsible for covering two gaps in the running game.

This is best described as a “read and react” system that leans on large and less-explosive linemen in order to succeed.

In other words, if you have two-gap responsibilities, you must dig in and hold ground until you diagnose which gap is being attacked. Then you must make your push, closing a gap with the opposing lineman and filling the other with yourself. This is dirty work.

One-Gap Defense

What many fail to realize is that all 3-4 defenses are not just two-gap (just like all 4-3 defenses are not just one-gap). Former Cowboys coach, Wade Phillips, employed a one-gap 3-4 defense that divided gap responsibilities amongst his front seven. With only one-gap responsibility, players were able to act much more quickly upon snap. Defensive linemen, specifically, were better positioned to make plays in the backfield.

Cowboys 3-4 one gap /

Look no further than former Wade Phillips player, J.J. Watt. It’s likely much of his talent and explosiveness would be wasted in a two-gap system, but in Houston, he is usually given only one-gap responsibilities allowing him to explode through the gap in a very proactive attack.

The Cowboys today operate primarily in a one-gap 4-3 system under Rod Marinelli.

Marinelli likes to use his “rushmen” as playmakers on the defense, and attack proactively, rather than react more passively.

As a result you see more backfield penetration from the front four as well as some big running plays against.

The Cowboys one-gap defense doesn’t ensure each gap is double-covered like many of the more-conservative two-gap systems. This is one of the reasons that Marinelli requires strong tackling from his defensive backs – especially his in-the-box (strong) safety.

Note: When Cowboys on the Chalkboard breaks down the defense in coming days, we will look specifically at the strong safety, Barry Church, and his role against the run.

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Hybrid One-Gap Defense

Because nothing can ever be black and white or the offense will expose it, the Cowboys do use some two-gap schemes mixed into their one-gap system. For lack of a better name, I call this the Hybrid. The Hybrid can assign two-gap responsibilities to some players, while giving one-gap responsibilities to other players.

Who’s the player most likely to receive a two-gap assignment?

The 1-technique defensive tackle.

We’ll get into outlining the defensive line techniques on the next Cowboys on the Chalkboard, but for now, I’ll just assume everyone has a basic grasp of the one-technique DT. Look at the chalkboard below. In it you can see a defense with a hybrid of both one-gap and two-gap responsibilities.

Cowboys 4-3 1-Gap Hybrid /

As you can imagine, there is no shortage of combinations regarding how Rod Marinelli can mix and match his gap responsibilities. He can do it with defensive tackles as well as with defensive ends. He can include LBs in both as well.

If the Cowboys are blitzing, some players must play two-gap. Other gaps could be completely neglected in a blitz, which explains why many coordinators uses blitzes sparingly.

Does the offense have a mobile quarterback? That also needs to be accounted for with extra gap discipline and possibly even a shadow LB over the top.

Adaptability is key because beating your opponent requires flexibility, deception, and execution. The Cowboys don’t play a very complicated defense, but it’s far from being vanilla and isn’t always predictable.

At the end of the day, the Cowboys run a 1-gap defense that asks it’s linemen to aggressively attack a singular gap, rather than sit back and read and react. That’s why Rod Marinelli refers to them all as “rushmen”. Run or pass they are coming.

Next: NFL Draft: Another Second Round Steal for the Cowboys This Year?

In the next Cowboys on the Chalkboard we will break down the defensive techniques and how their alignments are based on their gap assignments and the Cowboys’ overall defensive scheme.