Mind the Gap . . . and the Blitz

In today’s lesson we go from the big-picture, offensive side of the line of scrimmage to the in-the-trenches nitty-gritty on the defensive side.  Today, we discuss gap assignments and blitzes.

Gap Assignments

 

As we have discussed previously, the seven players closest to the line of scrimmage (LOS) before the snap of the ball are the defensive linemen and the linebackers.  The basic job of the defensive lineman is to try to break through the offensive line to put pressure on the quarterback or, better still, tackle the quarterback behind the LOS for a sack or tackle the ball carrier.  The linebackers, meanwhile, key on the running back(s) and tight end(s) and try to contain them, preventing them from gaining yardage.

So, if this is their job on every play, doesn’t the offense know exactly what each of these seven players will do when the ball is snapped?  Not necessarily.  Just as the offense calls a different play each time, the defense can also make changes from snap to snap.  One way they do this is by changing their gap assignments.  If you look at a diagram of the offensive line on a typical play, you see that there are physical gaps between each player on the offensive line.  Each gap is labeled by the defense in their game planning.  Here is an example that uses letters, a fairly typical method:*

Taken from: iSport.com, at http://amfootball.isport.com/amfootball-guides/gaps-holes-in-football.  Altered from original.

In this diagram, the gaps between the center and the left and right guards are called the “A” gaps.  The gaps between the guards and the tackles are the “B” gaps, and the gap between the right tackle and the tight end is the “C” gap.  The defense uses these gap designations to assign each defensive linemen and linebacker his own space to occupy for each play, called his “gap assignment.”

In addition to the gap he occupies, each member of the front seven can also be told on which side of each gap he should line up against.  This is done with numbers that signify the inside shoulder (i.e., toward the center of the offensive line) or outside shoulder (i.e., toward the sideline) of each offensive lineman, as shown below:

Taken from http://www.bleedinggreennation.com/2009/2/12/757415/football-101-defense-techn.

Therefore, if a left defensive tackle has the assignment B3, he has to line up across from the right guard’s outside shoulder and try to rush through the gap between the right guard and the right tackle.

 Blitzes

Gap assignments come are important for defenses and can change on every down, so the offense can’t always be prepared for the kind of pressure the front seven might bring.  Another way the defense can put pressure on the offense and, specifically, the quarterback, is with a blitz.  Simply put, a blitz is when a player that rushes the quarterback instead of doing his usual job on defense.  Blitzes are typically used when the defense believes that the quarterback is planning to pass the ball.  This will be obvious on many plays, either because it’s third down and the offense needs several yards for a first down, or because the offense has a lot of pass receivers on the field. 

On passing plays, the offense will usually have more players assigned to block the rush from the defense, to give the quarterback more time to throw the ball.  Using a blitz allows the defense to even out the number of players rushing the QB against the number of players blocking for him.  The most common blitz used is the linebacker blitz, where one (or more) of the linebackers rushes the quarterback instead of watching the running back or tight end.  Safeties and cornerbacks can also blitz, but this is less common.

Blitzes are often effective, but also have risks.  Because there are fewer players covering the receivers running down the field, the secondary needs to make sure they cover those receivers closely.  If they do not, the quarterback has an opportunity to find a receiver for a big gain in yards.

*Note, however, that this diagram depicts six linemen, probably to better illustrate the location of the gaps.  Usually there won’t be more than four linemen.