Zero the Mike & “What’s a ‘Belly-Key’?”

Double gap the Mike in a single gap scheme.

Zero the Mike

In a single-gap defense, the initial thought is to align the defender responsible for a given gap head-up in that particular gap. In theory, this makes it easy for the defender to read his keys and react to the ball aggressively. Offenses play on this alignment rule with zone blocking, particularly the Zone Read. As the ball snaps the offensive line steps in a certain direction, with the understanding that by moving the gap, the defenders will move too. In order for defenses to combat this, the defensive line and linebackers must react off each other (anchor points) and utilize gap exchange. By playing off anchor points (or D-Line gaps), the defense can confuse the offense and stay one step ahead.

In a 4-3 scheme’s Over Front, Mike’s gap responsibility is the strong side “A” gap and the Nose occupies the weakside “A” gap. By moving the Mike to a “Zero”, or head up position on the Center, he can “double gap” the fit while keeping his single gap integrity. Initially, this may sound oxymoronic, but when combined with natural gap exchanges called “belly-keys” the defense can double gap the Mike and Nose without actually making them responsible for two gaps. Usually, two-gaping is seen in the interior or in a 3-4 scheme. The Mike is usually double gapped in a traditional 4-3 scheme that leaves the OLBs outside the box (this is called the “pull-the-chain” method).

The “G” or 2i

By aligning the Nose in a 2i, or “G” technique, the Mike and Nose can play off each other, creating an advantage for the defense. Many 4-3 teams shade their Nose, but by putting him in a 2i it stresses the offense line. In a zone scheme, a 2i can wreak havoc if his main key is the center. This relationship can be used to make the Center wrong in a zone scheme. Below is a diagram of a basic Over Front versus a 10p 2×2 formation.

.01 4-3 Alignment

Exchanging Gaps

At the snap of the ball, the Mike will always take a step to his main gap (lead foot), the strong side “A”. In a gap exchange scheme, the Nose will push vertical in the weakside “A” and react off the Center. If the Center steps to the Nose, he will hold his gap and the Mike will insert himself in the strong side “A” against the run.

If the Center steps away from the “G”, the Nose will chase off the backside of the Center, essentially taking responsibility for the strong side “A”. This allows the Mike to rock back to the weak side “A” and stressing the weak side Guard because his technique tells him to latch on to anyone head up to outside. In theory, the weak side Guard will push, or chase, the Nose to the opposite “A”. The Center will have overplayed the Mike, leaving him free to fill the weakside “A”, and hopefully, make a 1-on-1 tackle. This technique is referred to as a “Belly Key.”

.02 Belly Key

The Nose creates a natural cutback for the RB. The only problem? The Mike is rocking back unabated to the open gap. Below is a look at how Baylor plays with gap exchanges against zone blocking. Watch how aggressive both inside linebackers can be to the ball while being patient and allowing the defensive line to clear out the mess in front of them. Once the LBs realize the play is a zone, they can focus their attention on the mesh point. The QB opens to the boundary while the zone flow is to the field.

Knowing that the D-line will wash and the QB will most likely pull it, the LBs can now be aggressive to the flow. One key element is the use of the Pistol. In the Pistol offense, the Qb’s initial direction is where the read is (no need to worry about a “flop read”). This technique allows the ILBs to become unblockable because the offensive line cannot climb to the next level.


By “zeroing” the Mike, and aligning the Nose in a 2i, the defense can double gap the “A’s” and create havoc to an offense’s zone scheme. In the run game, a defense always wants to create plus-one situations. Aligning the Nose in a “G” allows him to read the Center and either hold his gap, or close down the opposite “A”. Anytime the Mike sees the Nose flash in front of him he adjusts his steps and attacks the opposite gap. The “Belly Key” can be a nice addition to any defense that sees a lot of zone blocking and can be used with any front.

** To note, offenses can counteract this by running a “Bang” or man/zone scheme. In this play, the Center “bangs” the shoulder of the 2i, hopefully knocking him off balance and giving time for the weak side Guard to overtake. The Center then sifts to the Mike and blocks him according to his departure angle. The back tries to hit the hole off the Center’s backside. **

More from MQ: Using Natural Gap Exchanges in Your Front Seven

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Author: MatchQuarters


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