Defense · Gaps & Run Fits
Gaps & Run Fits
Good run defense is a team effort. The defense tries to account for every possible running lane so the ball carrier has nowhere clean to go.
Start Here
What Is It?
The spaces between offensive blockers are called gaps.
When the offense runs the football, those gaps are potential paths for the ball carrier.
The defense must make sure those paths are accounted for.
A GAP
The spaces between the center and the guards.
B GAP
The spaces between the guards and the tackles.
C GAP
The spaces outside the tackles, or between a tackle and tight end depending on the formation.
A defender's responsibility against the run is commonly called his run fit.
The goal is not simply to have everyone chase the running back. The defense wants its players working together so that one defender's position complements another's.
The Big Idea
Good run defense tries to make sure every potential escape route has an answer.
Football Watching 101
How It Works
Imagine the running back receives the football and looks for an opening.
He may try to run inside through an A gap, attack a B gap, bounce toward the C gap or continue all the way outside.
The defense wants players responsible for those areas.
CONTROL INSIDE
Defensive linemen and linebackers work to close interior running lanes.
SET THE EDGE
An outside defender prevents the runner from easily escaping around the defense.
RALLY TO THE BALL
Other defenders pursue so the runner has fewer places to escape.
The exact responsibility depends on the defensive call. A defensive lineman may control a gap on one play while a linebacker is responsible for that area on another.
That is why run defense should be viewed as a connected system, not simply a collection of individual tackles.
Learn The Gaps
The gaps are named from the center outward. Defensive run fits determine which defenders are responsible for preventing the ball carrier from finding an open lane.
Simplified gap map — formations with tight ends and different blocking surfaces can change how coaches describe the outer gaps
The Reason
Why Teams Use It
The offense is trying to create an open running lane.
The defense is trying to eliminate it.
If every defender simply runs toward the football, the offense can use blocking, misdirection and the runner's movement to create an enormous opening somewhere else.
Run fits give the defense structure.
One defender may attack an interior gap while another protects the neighboring gap. An EDGE defender can prevent the runner from simply escaping outside.
Safeties can also become part of the run fit, especially when they move closer to the line of scrimmage.
When everyone performs his responsibility correctly, the runner may see what appears to be an opening disappear almost immediately.
When someone misses his fit, however, the result can be a large open running lane.
Remember These
Run-Defense Terms You'll Hear
A Gap
The interior gap between the center and guard. There is an A gap on each side of the center.
B Gap
The gap between the offensive guard and tackle. There is a B gap on each side of the formation.
C Gap
The area outside the offensive tackle, or between the tackle and a tight end when that blocking surface is present.
Run Fit
A defender's responsibility within the structure of the run defense. The defense coordinates these responsibilities so potential running lanes are accounted for.
Set The Edge
An outside defender maintains leverage that makes it difficult for the runner to simply escape around the outside of the defense.
Force Defender
A defender responsible for influencing the ball carrier away from an easy outside path and back toward help. Exact force rules vary by defensive system.
Spill
A defensive technique or philosophy that can force the ball farther outside toward another defender rather than allowing it to hit cleanly inside.
Cutback
When a runner begins in one direction but finds an opening back toward the opposite side. Disciplined backside defenders help prevent large cutback lanes.
Backside Pursuit
Defenders away from the initial direction of the run continue pursuing the football so the runner cannot easily cut back or escape.
Gap Integrity
The idea that defenders maintain the structure of the run defense rather than abandoning responsibilities and creating an open lane.
Watch The Game Differently
What Should I Watch For On Saturday?
Watching run fits is one of the fastest ways to start seeing football differently.
Instead of watching only the running back, look at the defense immediately after the snap.
Watch The Running Lanes
Who controls the inside gaps?
Which linebacker attacks the opening?
Who is setting the outside edge?
Is there a defender waiting for the cutback?
Where does the running back finally choose to go?
Pay special attention when a run suddenly breaks for a big gain.
Go back and look at the space the running back entered.
Was a defender blocked out of his gap? Did a linebacker attack the wrong lane? Did the EDGE defender get moved inside and allow the runner outside? Did the backside lose contain on a cutback?
Now watch a run that gains almost nothing.
You may notice something completely different: every time the running back looks for another lane, another defender is waiting.
That's good run defense.
It may look like one player made the tackle, but the other ten defenders may have helped determine where that tackle happened.
Your sequence is: Find the intended lane → Watch the run fits → Check the edge → Look for the cutback → See where the runner is forced to go.
Keep Learning
Related Concepts
Defense Lesson 4
Man Coverage
Now move behind the defensive front and learn what happens when defenders are assigned to cover specific offensive players.