Before discussing the zone blitz it is necessary to briefly discuss the idea of blitzing.  I consider a blitz to be any defensive play when the defense sends five or more defenders against the quarterback.  Just like any type of football defense a blitz can either be classified as a man or zone blitz.  In man coverage the defenders are responsible for covering a particular receiver in zone coverage the defenders are responsible for a certain area of the field.

The offense can have a maximum of five eligible receivers and will also have one quarterback and five offensive linemen.  A man defense needs to be able to account for each one of these receivers by assigning at least one defender to each receiver.  If a receiver stays in to block the defender responsible for him can either drop into coverage or blitz the quarterback.  Therefore the in a man blitz the defense can always blitz one more defender than the offense can account for.  This is because the offense cannot have the quarterback both block and throw.  Below is an image from Madden 10 showing this concept:

via www.mymaddenpad.com

Notice that six defenders are assigned to blitz and the other five in man.  No matter how many men the offense keeps in to block the defense will be able to send one more after the quarterback.  For example if the offense blocks the fullback (Y) the defense will just blitz the free safety (who is matched up with him in man).

There is a major problem with this defense even it does send a free defender, as the great Dick LeBeau (defensive coordinator of the Pittsburgh Steelers) said, "if one [defender] slips or if [the offense] springs a guy somewhere, there’s no one left as a second line of defense to keep a 15-yard gain from becoming a 60-yard gain."

Here is a video of Colt McCoy throwing a touchdown against a man blitz being run by Ohio State in the Fiesta Bowl: (Chris Brown of Smart Football diagrams the offensive play here http://smartfootball.com/passing/colt-mccoys-texas-passing-game)

Now even with the major risk associated with a man defense blitz defenses still want to be able to blitz the quarterback.  The solution is the zone blitz.  Dom Capers (defensive coordinator of the Green Bay Packers) said the zone blitz is "a way to put pressure on the quarterback and yet not have as much risk involved as if you’re locked up with a man. It’s not as defined for the quarterback to read because you’re passing receivers [from defender to defender], as opposed to being clearly locked up on a receiver. We think it gives us some ability to create confusion and indecision on the part of a quarterback."

For zone defenses to be able to adequately defend the field they must have at least six defenders in zone coverage, but for a defense to be counted as a blitz five or more defenders must rush the quarterback.  This makes the numbers pretty simple for the defense.  Five defenders will rush the quarterback and six will drop back into zone.  The complicated part is where the defenders blitz, where the defenders drop into zones, and which defenders do which.

To understand the zone coverages behind a zone blitz it is first necessary to understand zone coverages.  For the purpose of this article I will only explain two zone coverages (I will write a piece in the future that goes far more in depth with the different kinds of zone defenses) the two-deep and three-deep zone shells.

In the two-deep zone defense there are two defenders who defend the deep portion of the field; typically this is done by the two safeties.  These defenders split the deep portion of the field into halves; each player is then responsible for one half of the field.  The other four or five defenders in zone coverage (in this case it will be four defenders) split the shallow areas into fourths or fifths; each defender is then responsible for a fourth or a fifth of the shallow part of the field.  Below is a diagram of a two-deep zone defense with seven defenders in coverage:

via espn.go.com

In the three-deep zone defense there are three defenders who defend the deep portion of the field; typically this is done by the free safety and the two cornerbacks.  These defenders split the deep portion of the field into thirds; each player is then responsible for one third of the field.  The other three or four defenders in zone coverage (in this case it will be four defenders) split the shallow areas into thirds or fourths; each defender is then responsible for a third or fourth of the shallow part of the field. Below is a diagram of a two-deep zone defense with seven defenders in coverage:

via espn.go.com

With all the presnap motion common to most zone defenses and the fact that the cornerbacks need to quickly drop into shallow zones it is hard for the defense to properly bump the receivers.  This means that a two-deep zone shell would leave to many voids downfield for the receivers to run into.  Most zone blitzes end up coming out of a three-deep zone shell.  This is because as Dick LeBeau said "The zone blitz is a conservative way to blitz, really.  Percentage-wise, it’s the safer way to blitz. That’s what we were looking for all along when we started out."  More specifically in a three-deep zone blitz three defenders will split the field into thirds and three defenders will split the shallow part of the fields into thirds as well.   These type of zone blitzes are known as fire zone blitzes and are they type of zone blitzes run by the vast majority of teams.

via www.everydayshouldbesaturday.com

These zone blitzes do not usually look like zone defenses while being run by the defense.  The defenders who are covering the shallow thirds of the field do not just guard an area of the field.  Instead they read the patterns being run by the receivers, this is called "pattern reading" and is something that Nick Saban, head coach at the University of Alabama, is famous for.  This makes it appear as if the defenders are playing the receivers in man coverage.  Further, if the corners are dropping back into deep coverage (at least one cornerback is always dropping into deep coverage because these are three-deep zones) they are taught "press-bail" technique.  This means the cornerbacks line up over the receivers as if they were going to play bump-and-run coverage and then drop into deep coverage.

However, simply assigning five defenders to rush the quarterback and assigning another six defenders to drop back into zone does not ensure a successful zone blitz.  There are two more aspects present in most successful zone blitz schemes.

First, a defender must drop into zone where another defender is blitzing from.  In the diagram below the free safety "drops down" this means he is initially given a deep alignment, but immediately before or after the snap he "drops down" into the front seven to cover a shallow zone.  In this case the free safety is covering the shallow zone right behind the blitzing weakside and middle linebackers.  If this were not done (dropping a defender into coverage behind the defenders) the quarterback would know there would always be a hole in the coverage right behind the blitzers (a defender cannot both blitz and drop into zone).

via espn.go.com

Secondly, a defender (usually a defensive lineman) will pretend to blitz and then drop back into coverage.  This is done for two reasons to occupy an offensive lineman or other player assigned to pass protection for the offense and to confuse the quarterback.  The defender will often take one step towards the quarterback and then drop back into coverage.

This first step by the defender forces an offensive lineman (or any other blocker) to commit to blocking this defender.  However, when the defender drops back into coverage the offensive lineman is left "blocking air" and is wasted for the play.  This is essential for obtaining the numbers advantage that is essential in football.  Remember the defense is only blitzing five defenders, so if there was no confusion among the offense they could easily block the blitz with their five offensive linemen while still sending out five receivers.  If a defender can force an offensive lineman to "block air" than the defense is rushing five defenders against only four blockers (assuming that the offense is not blocking any backs or tightends) and has a numbers advantage.  In the imagine below notice number 72, Stapleton an offensive lineman for the Steelers is blocking nobody while Ray Lewis closes in on Ben Roethlisburger for the sack.

via assets.sbnation.com

The defender who is pretending to blitz not only confuses the blockers, but also the quarterback.  As I mentioned above most quarterbacks are taught that if they read a zone defense pre-snap the area where the blitzers are coming from will be open.  This is because a defender cannot both blitz and drop into coverage.  The quarterback will then see a blitzing end or linebacker and assume that area of the field will be open only to throw the ball right into the defenders hands when they drop into coverage.  This explains how you can see things like this:

via cache2.asset-cache.net

Now that I have explained the basics behind a zone blitz I will walk you through a few of them.

The first is the middle and weakside linebacker cross blitz that is diagrammed above.  Here is the play diagram again:

via espn.go.com

This blitz shows all of the main parts of the zone blitz we have discussed above.  First, this blitz is a fire zone blitz as there is three-deep zone shell with three defenders in shallow zones.  Second, we can see the free safety "dropping down" behind the blitzing linebackers.  Third, we see the weakside defensive end fake blitzing and dropping into coverage, which forces the left tackle to "block air". 

We also see something common to most zone blitzes which is the crossing of the linebackers blitzing angles and the stunting of the defensive linemen.  This is meant to further break down the same pass protection just like the fake blitzing of the weakside defensive end.  The defensive linemen are blitzing the outside shoulders of the offensive linemen they are aligned over; this should force the linemen to turn at angle to block the defensive linemen.  Making the offensive linemen turn creates bigger gaps for the linebackers to rush through.  The crossing of the linebackers accomplishes the same thing right guard will turn to block one linebacker creating a very clear lane for the other linebacker straight towards the quarterback.  Below is video of the Green Bay Packers running this play against Minnesota Vikings: (the play is actually flipped in the video, so it is middle and strongside linebacker blitz)

The next blitz is middle linebacker nickleback blitz.  This blitz is done out of a nickel package (meaning there are five defensive backs, three corner and two safeties).  Below is the same blitz diagrammed with the strongside linebacker blitzing instead of the nickleback.

via www.everydayshouldbesaturday.com

This blitz shows a perfect example of a safety "dropping down" notice how at about -2:20 the nickleback slides in towards the offensive line and the safety drops down over the slot receiver.  This does three things, it allows the safety to more easily cover his shallow zone, the nickleback has shorter to run while blitzing the quarterback, and the defense appears as if it could still be a man coverage base defense.  Notice the weakside defensive end dropping into coverage and the defensive lineman stunting towards the weakside.  Here is the video:

That’s about it for zone blitzes hope you learned something.