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Why gaps are the most important building blocks of every play

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Once you understand the ABCs of football, you can begin to understand anything else about the sport as well.

You don’t need to be a master football tactician to be able to see and appreciate little things on the field. For years you’ve watched your team play a dozen or so games per season, and you’ve watched their opponents. You may not realize it, but you’ve been conditioned to understand football fundamentals; you just need to be able to put names to what you’re seeing. We’re here to help with that.

This isn’t so much an explainer of how to play or coach the sport as it is how to watch the sport. I’m not a coach and you’re (probably) not a coach if you’re reading this, so we should just talk to each other like not-coaches, while using slightly elevated language to explain the stuff we see on the field.

First up, the literal ABCs of football: gaps.

What are gaps, in three sentences or less, because I’m not reading this whole thing? The (insert letter) gap names the space between two offensive linemen. Either side of the center is A, and then we work out from there until we run out of players on the offensive line.

So there are two A-gaps? How do we tell them apart?

Yep. There are two. We’ll come back to that in a bit.

Wait, so that’s it? Football people are obsessed with making football sound more complex than it really is.

A typical distance between offensive linemen is two to three feet (that’s called a split). But that can vary from scheme to scheme, as well as specific game situations. An air raid offense may have slightly wider splits, in order to get the defensive line more spread out pre-snap. An offense may tighten their splits in order to create more space outside of the offensive line to get their speed in space quicker on a toss play for instance.

How is this gap thing applied to an offense I’m watching? I like to use it as a shorthand to explain where a play’s going.

Let’s pretend Baker Mayfield was going to hand this ball off to his running back, Rodney Anderson, who was going to then run to the left.

The left would be the “playside” or “front side” (aka where the play is intended to go).* If the Sooners are running inside zone to the left, then Anderson will have an aiming point that he’s supposed to run toward at first. It depends on the specific scheme, but a common landmark for the running back, on inside zone, is the outside of the play-side guard’s butt.

So I could tell you this play is going toward:

  • to the outside of the playside guard’s butt and inside the playside tackle, OR
  • to the B-Gap on the left

You tell me what’s easier to understand and convey.

*[Yes that’s coach speak. The play could cutback and go the other way or even bounce outside.]

So how do I apply this to the defense?

There aren’t defensive B-Gaps or offensive B-Gaps. There is only The B-Gap, and it’s between the guard and the tackle. This is a trench term, and can be extended only as far as the widest person on the offensive line (usually a tackle or a tight end). If a wide receiver is blocking on the outside, there isn’t a P-Gap.

On the opposing side, defenders have a gap to control. Blitzing can really be thought of, in its most basic form, as how defenses try to screw with the offense, by switching or adding gap responsibilities to either confuse or outright overwhelm protection with more than four rushers.

Perhaps the most famous defensive play is the double A-Gap blitz, the brainchild of former Eagles defensive coordinator Jim Johnson. The name’s self-explanatory now that you know what the gaps mean, right? Let’s try to spot it in the wild.

As a defender, you don’t have to be initially lined up across from a particular gap in order to be responsible for it once the ball is snapped. Some defenses even ask their linemen to be responsible for two gaps at once, by reading the play and reacting. On this play, the two interior defensive linemen actually widen, to enable the linebackers to waltz through either A-Gap. One of them is lined up in the A-Gap at the start of the play, but by the time it’s over, he’s essentially traded gaps with the linebacker behind him:

In football, interior pressure is more effective for a few reasons. One of them is because the shortest straight line to any quarterback is right through the A-Gaps.

Exhibit A:

Ok, but my team doesn’t blitz all the time. What about on the plays where they don’t?

Defensive linemen can run stunts to swap gaps with just each other to mess up what the offensive line is doing all on their own. In a perfect world, defenses want to create this picture whether they use a stunt or not:

Replace the letters with defensive players, and it looks like what the Patriots did the Rams’ running game in the 2019 Super Bowl.

Offenses have always tried to find ways around how defenses try to stop them — that is quite literally the point of their existence — and the beauty of the zone read is that it offers a simple, yet elegant way to just create an extra gap that must be accounted for by the defense. If the RB is going to the right here, then the defense has this defended from a numbers perspective, right? Three defenders for three gaps?

Not so fast, my friend.

By involving the quarterback, the zone read creates that extra gap on the backside in the running game. If the end crashes down the line of scrimmage to chase the running back, then the quarterback reads it, pulls it, and runs around him. The quarterback “blocks” the edge defender without touching him.

In a scenario like this, we would call this being outgapped. It’s easy to see when this happens. He’s in no man’s land, and then an athlete like Marcus Mariota breaks his ankle, then houses it.

Anything else?

Of course there is. You can spend all the time we have left until the heat death of the universe drilling down on one play. But this is how one of the most simple ideas about the game of football can inform how we look at virtually every game we’ll watch on any given Saturday.