Posted: July 17th, 2012

Don Coryell and Bill Walsh were two pioneering and aggressive innovators who greatly expanded how people approached the NFL offense. As I wrote in a recent piece about the evolution of the offense, both men challenged standard beliefs and conventional wisdom, helping to gradually transform the run-dominated league that Vince Lombardi ruled in the 1960s into the pass-heavy NFL we know today. More than 30 years after Coryell and Walsh first advanced their strategic views, their influence remains as strong and pervasive as ever.

But how did defenses react to these historic changes in offense? Remember that, for years, defensive coaches had been trying to stop offensive formations that almost exclusively featured two backs, two wide receivers and a tight end aligned on the line of scrimmage right next to the tackle. Passing was predominantly a long-yardage tactic, focused on deep, seven-step drops and long-developing routes. The defensive template was fairly well-established, consisting of 4-3 fronts that rarely blitzed, minimal coverage schemes that highlighted man-to-man with deep safety help and basic zone concepts that did not incorporate route progressions or pattern reading. When teams did blitz — and a blitz back then was always defined as sending five or more rushers — they played man coverage, working without a deep safety in the middle of the field most of the time. The rewards could be great, but so were the risks.

Unless they had great talent, defenses of that era (and in the early 1980s) were not strategically equipped to effectively respond to the expansion of the passing game, with its innovative emphasis on quick timing throws, three-receiver sets and tight ends that could align outside the formation. Thanks to Air Coryell, Bill Walsh and the proliferation of the West Coast offense, offenses were usually a step ahead. Teams needed to make a parallel change in defensive philosophy. As quarterbacks became increasingly important to their offenses, stopping them became increasingly important to defenses. The challenge was to exert pressure on the quarterback without placing too many demands on the coverage. Conventional thinking about blitzing held that pure man coverage be used. Cornerbacks had no help; they were exposed, liable to give up big plays and touchdowns if they were beaten on the outside.

Dick LeBeau, the defensive backfield coach for the Cincinnati Bengals from 1980 to 1983, recognized this significant shift. He intuitively understood that the objective was to impact the quarterback without sacrificing bodies in coverage. It was a numbers game: Teams had to rush with fewer defenders while forcing offenses to keep more blockers in pass protection, including eligible receivers like running backs and tight ends. The goal was to have more defenders available to cover fewer receivers. LeBeau addressed the need to bring pressure by attacking specific areas of the pass protection. He overloaded one side of the protection with more rushers than could be accounted for, often while rushing no one from the other side. He did not increase the number of pass rushers; in fact, he reduced them. He deployed fewer rushers, never more than five (even, at times, four), in a more strategic manner. It was a safer way to blitz that left units exposed to less risk on the back end. These two elements were the building blocks of the zone blitz concept. LeBeau was not the first to utilize zone blitz schemes. But just as Coryell and Walsh revolutionized the passing offense, LeBeau forever changed pass defenses in the NFL.

LeBeau always made it clear that the quarterback was his target. He wanted to slow down his thought process, delay his reads, make him hold that trigger for just an extra beat or force him to inadvertently throw the ball toward defenders. Creating the illusion of pressure, the perception of pressure, was paramount. This could be better accomplished with a 3-4 front than with a 4-3. The 3-4 featured a fourth linebacker instead of a fourth lineman, giving coordinators an additional mobile player with which to disguise their intentions. Having fewer defensive linemen and more linebackers on the field allowed coordinators to be more versatile and flexible with their schemes, creating more-effective illusions of pressure.

The conventional rush and coverage responsibilities of defensive players were exchanged. Linebackers and defensive backs became blitzers, while linemen dropped into pass coverage, defending designated areas vacated by the blitzers. The overriding premise was to create confusion for the offense and make it difficult to identify who was rushing and who was dropping. This concept was the crux of the zone blitz. It created protection uncertainty in the offensive linemen and backs, and stoked coverage hesitation and doubt in the quarterback. I can’t tell you how many times I’ve seen three offensive linemen block a solitary defensive lineman on one side of the line while two offensive linemen and a running back are left to handle four pass rushers on the other side. In those cases, the offense has lost the numbers game, and a rusher usually finds a clean path to the quarterback.

Multiplicity in pre-snap alignment creates the illusion of pressure from different areas of the defense; post-snap movement breaks down the pass-protection schemes. That was why defenses were successfully able to use the zone exchange/blitz concept to speed up and pressure quarterbacks even when there were fewer rushers on the field than pass protectors. Defenses weren’t always able to get an unblocked player to the quarterback, but they did get a linebacker matched up against a running back, which was often the objective. Outside linebackers who can rush the pass are critical to 3-4 defenses; they must be able to defeat backs in one-on-one matchups. The Pittsburgh Steelers have certainly had their share of such players during LeBeau’s time with the team, including James Harrison and LaMarr Woodley.

The coverage element was just as important. LeBeau believed in taking the less-risky approach, one that minimizes the chances an offense can make explosive, game-changing plays if the secondary is beaten. The coverage element was based on a matchup-zone principle, derived from a complete understanding of route combinations and route progressions based on receiver alignments. All combination routes have a symmetry and design that can be understood using simple mathematical concepts. The coverage was structured on angles and leverage; LeBeau saw it as a geometric equation, having his players defend areas, or squares and triangles, depending on the specific combination routes. That approach led to coverage that proactively, aggressively attacked and jumped routes, even though it was premised on zones. It rested on man-to-man reactions within the framework of a zone concept, with deep safety help always part of the formula.

Quarterbacks struggled to decipher the underneath coverage. When defensive linemen dropped into coverage, the quarterback saw them in places he didn’t expect to. Again, a moment of hesitation and uncertainty was created. The quarterback was put into a confusing, contradictory mindset. Reading a potential blitz before the snap, the quarterback would initially increase his tempo, then be goaded into indecisiveness by the coverage exchange. Forcing the quarterback to think too much will help the defense win more often than not.

Over time, the initial zone blitz model has evolved and expanded. It has become particularly prevalent in nickel and dime sub-packages, which feature quicker and more versatile athletes on the field. It is much more difficult for an offensive lineman weighing more than 300 pounds to react to a blitzing safety or slot corner, especially when his initial focus is on the defensive linemen directly in front of him. Defensive coaches have seen the value of having more players stand up and move around before the snap. That increases the mental — and, by extension, physical — burden on both individual blockers and protection schemes. In addition, the coverage component has become more varied. I see man-to-man, I see hybrid coverages that incorporate both man and zone and I even see some elements of “cover zero” when the defensive coordinator feels confident that he can get a free rusher to the quarterback.

The NFL game is constantly changing. I see new wrinkles every week in my film study. Yet defensive coaches remain steadfast in their goal: finding ways to pressure the quarterback without risking too much in coverage. Very few teams can do that while rushing just four defensive linemen. The focus is on deception and disruption. Those are the driving principles of the zone blitz, and another reason for the chess match to continue.

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