Down 17 points early in the fourth quarter of their Week 2 game against Houston, the Jaguars were pushed to desperation. Hoping to start a comeback, Jacksonville lined up with four wide receivers for second-year quarterback Blaine Gabbert. The Texans defense, orchestrated by longtime NFL head coach Wade Phillips, countered by bringing a blitz. Linebacker Bradie James joined the Texans’ front in its pursuit of Gabbert, and as Houston’s line twisted and slanted their way to the quarterback, the extra rusher allowed defensive end J.J. Watt to get free and bring Gabbert to the ground.

The sack, like most outcomes in football, was a product of some other, often unnoticed factor. Watt gets the credit, but without James’s disruption, he would not have been able to bring down Gabbert. And the ripples go further than that. The other reason for Jacksonville’s faltering has nothing to do with rushers. Despite having four wide receivers running routes, no one was open. Phillips had called for a blitz, and although Gabbert was surrounded by Texans, it was the coverage that sealed his fate.

The word “blitz” is maybe the most exciting word in football. Like a football Mexican standoff, it conjures up the ultimate him-or-me scenario — a mass of defenders in single-minded, blind pursuit of the quarterback, and an offense that knows it might be only a missed tackle away from a long touchdown. Former Florida State football coach Bobby Bowden once gave a clinic lecture about the blitz aptly (and neutrally) titled, “Hang Loose — One of Us Is Fixin’ to Score.” A blitz is the closest thing we have to football bedlam.

Phillips’s call wasn’t quite bedlam. The “zone blitz” Houston brought combines the do-or-die nature of a traditional man-to-man blitz with a more conservative zone coverage behind it. Zone blitzes are not particularly new, but while the “blitz” element continues to receive the most attention, it’s the continuing changes in the coverage behind it that make zone blitzes the most important defensive tactic in modern football.

In the mid-1980s, defenses across the NFL faced a common problem: how to stop the precision-passing offenses becoming so prevalent throughout the league. Most notably, it was how to stop the San Francisco 49ers, led by resident NFL offensive genius Bill Walsh. Walsh, one of the most meticulous men football has known, had studied the passing game with and under some of the game’s masters — Paul Brown, Sid Gillman, and Al Davis — but had taken the next step by planning every detail, every subtle movement by quarterback, offensive line, and receiver. Walsh transformed passing from a combustible, high-risk, high-reward strategy into something certain and predictable. His quarterbacks completed a higher percentage of their passes, didn’t throw interceptions, and didn’t take sacks. He’d kept the reward and reduced the risk, and defenses needed an answer, fast.

Walsh’s protégés were hired around the league. One of them, offensive assistant Sam Wyche, became head coach of the Bengals, and upon his arrival enlisted Cincinnati defensive backs coach Dick LeBeau as his new defensive coordinator. As Tim Layden explains in his book, Blood, Sweat and Chalk, LeBeau had experimented with the idea of combining a blitz with zone coverage prior to Wyche’s arrival, and when the new head coach endorsed the idea, the zone blitz became LeBeau’s focus as a defensive coordinator.

For advice, he traveled to Baton Rouge to meet with Louisiana State University head coach Bill Arnsparger, a well-known defensive guru. Before he got to LSU, Arnsparger coached some of the NFL’s greatest defenses, first with the Baltimore Colts in the ’60s and later the Miami Dolphins — both teams led by Don Shula. He and Arnsparger won two Super Bowls in Miami, where Arnsparger coordinated the famed No Name Defense. One of those Dolphins defenders — he in fact had a name: Bob Matheson — was a linebacker whom Arnsparger began using as a defensive end in their 4-3 scheme, an early predecessor to today’s hybrid defenders. Together, Matheson and Arnsparger sparked two of football’s most enduring defensive tactics: the 3-4 defense and, maybe even more important, the zone blitz.

“With Bob there, with linebacking skills,” Arnsparger told Layden, “we were able to rush five guys and cover with six. That’s what you need to run a zone blitz.” Arnsparger continued to develop the zone blitz through the early 1980s, later relying on converted linebacker Kim Bokamper as the versatile defensive lineman who could drop into coverage. By the time he left for Baton Rouge — and long before he would coordinate a defense in his sixth Super Bowl, this time with the San Diego Chargers — Arnsparger had refined his theory of the zone blitz. As he explained in his book, Arnsparger’s Coaching Defensive Football:

What makes the zone blitz successful is that it allows the defense to bring outside linebackers and safeties to one side or both sides without using man-to-man blitz coverage. Normal blitzes use man-to-man coverage. The offensive line and one or two backs are assigned to block the defensive line and linebackers. In the zone blitz, the linebacker blitzes along with a secondary player, but the offensive pickup is different. It is different because defensive linemen who usually rush are now dropping out to short inside zones to replace the linebacker and secondary player that blitz. Because of the blitzer’s path, it is difficult for the offensive linemen to adjust.

LeBeau had clearly come to the right man. Not only was Arnsparger employing the types of tactics at the college level that LeBeau wanted to bring to the pros, but — true to form — Arnsparger had thought through the entire theory of the tactic as well. “Bill’s catchphrase was that he wanted to get ‘safe pressure,’ on the quarterback,” LeBeau told Layden. “And that expression stuck with me because that was a very succinct way to summarize exactly what I was looking for. Safe pressure. I walked out the door saying those words to myself.”

LeBeau, currently the defensive coordinator for the Pittsburgh Steelers, has, like Arnsparger, had his strategies vindicated by his success. To go with his Super Bowl rings and the success of his own protégés, LeBeau is a member of the NFL Hall of Fame. For the last quarter-century, innovations by Arnsparger and LeBeau have been the one counter to a football world full of would-be Bill Walshes determined to show off their offensive genius. Today, the zone blitz is ubiquitous, and the accolades recently — and rightly — afforded to LeBeau confirm what many already know.

LeBeau’s trip to the bayou is only half the story. The other half comes from about 10 years ago. Unsurprisingly, those would-be Bill Walshes — and even Bill Walsh himself to some extent — did not simply concede defeat to LeBeau’s newest tactic. Instead, offenses tried to find ways to counteract it. “I always felt that we contributed greatly to the development of the run-and-shoot offense,” said LeBeau. “Teams were just looking for quicker and quicker ways to attack, to the point where it might not even matter where the pressure was coming from.” He’s right. The run-and-shoot offense, as well as later iterations of spread offenses, arose in a world replete with zone blitzes, and much of their design centered on identifying and exploiting any weaknesses those blitzes left.

The biggest of those weaknesses came from what was originally a strength — the zone coverage behind the blitz. Many of the earliest zone blitzes Arnsparger called in Miami were not actually “blitzes” as we think of them now. The Dolphins would rush only four players in total, simply swapping out a rushing linebacker for a zone-dropping defensive lineman. As a result, these defenses were just as sound against the pass as zone defenses that had been run for the past 50 or so years. Defenders dropped to a spot, watched for a receiver in that area, and broke on the ball as it was released. Even with the threat of blitzes, quarterbacks eventually started exploiting the many soft spots on the field.

Nick Saban, currently the head coach at Alabama, was the defensive coordinator under Bill Belichick when the two were with the Cleveland Browns in the early 1990s. While speaking to high school coaches at a recent clinic, Saban summed up the early problems of traditional spot-dropping zone coverage: “Well, when Marino’s throwing it, that old break on the ball shit don’t work.”

The answer that Saban, Belichick, and many others developed was “pattern-match” coverage — essentially man coverage that uses zone principles to identify the matchups. As Saban explained at the 2010 Coach of the Year Clinics Football Manual clinic:

You can play coverages in three ways. You can play zone, man, or pattern-match man. Pattern-match man is a coverage that plays the pattern after the pattern distribution. That means you pick up in man coverage after the receivers make their initial breaks and cuts. We number receivers from the outside going inside. If the number-one receiver crosses with the number-two receiver, we do not pick up the man coverage until they define where they are going.

In other words, the zone blitz had come full circle. What began as a way to blitz without playing man coverage had started incorporating man coverage all over again, this time in an entirely new way.

Using pattern-match principles allowed defenses to overcome the deficiencies in both the manic, risk-heavy man-to-man blitzes and the easy-to-exploit soft spots in the zone-coverage scheme. There was now a way to keep the safety of the zone and the tighter coverage of man-to-man. Defenses had finally done for blitzing what Walsh had done for passing — keeping the reward but eliminating the risk.

The nuances of a pattern-match zone blitz are, as one would guess, rather extensive, but the principle is simple. “I had the opportunity to work for [current New Orleans Saints defensive coordinator] Steve Spagnuolo,” said University of Pittsburgh secondary coach Matt House at a coaching clinic in Pittsburgh this past summer. “He had a great analogy talking about zone pressure. He said, ‘All you do is roll out the basketball and tell the players to play three-on-three.’ The players will talk, communicate, and switch on the picks. We do the same thing in zone-dog coverage.”

The most common modern zone blitz is the “fire zone,” a five-man blitz behind which the defense plays coverage with three defenders deep and three underneath. The only limit to the countless arrangements of the five blitzers is a defensive coordinator’s creativity, but the coverage assignments are more finite.

Although the idea of pattern-match coverage is to defend the offense after the receivers show their routes, it’s still useful for the defense to identify where the receivers are when they line up. Against the Texans, the Jaguars lined up in a basic four-wide-receiver set with two wide receivers to each side and running back Maurice Jones-Drew lined up to Gabbert’s left.

The three deep defenders essentially divide the field into thirds, with the cornerbacks effectively playing the outside receivers — the first receivers from the sideline — on any downfield routes. Were these outside receivers to run immediately to the inside, however, such as on a shallow crossing route, the corner would make an “under” call and play his deep third zone like a traditional zone player. If that outside receiver moves far enough inside to become the innermost receiver in the pattern distribution, he becomes the middle linebacker’s responsibility, a coverage known as “no. 3.”

The most interesting assignment goes to the outside, underneath defenders, labeled in the diagram as “SCF/Seam” but also known in the NFL as “Bronco” coverage players. These are the true pattern-match players, and they have the toughest job. It’s their responsibility to determine whether the play is man, zone, or some combination thereof, all based on what is most favorable to the defense.

Fire zones are essentially three-deep coverages, and offenses have known how to attack three-deep coverages for years. There are two common methods of doing so. The first is sending four receivers vertical, with the idea being that three deep defenders shouldn’t be able to play four deep receivers. The second is sending the outside receiver vertical while the tight end or slot runs a deep out or a curl/flat combination. The pattern-match fire zone therefore is specifically designed to handle these tactics. Broadly speaking, these “SCF/Seam” or “Bronco” defenders will play man-to-man on the second receiver from the sideline so long as he runs vertically down the seam or runs a deep out of any kind. If the receiver breaks hard to the inside, the Bronco defender passes him off to the inside defenders and looks for another receiver coming through his zone.

“SCF” and “Seam” are the two most common methods of teaching this technique. “SCF” stands for Seam-Curl-Flat, and literally tells the defender the order of his priorities: Watch the seam, drop to the curl area, and let the quarterback’s throw take you to the flat. The SCF technique is played from inside to out.

The “Seam” technique, which is Dick LeBeau’s now-preferred method, works much the same way as SCF, only from the outside in. The theory is that in the NFL, if the defender isn’t aligned to the outside, the quarterbacks are so good that they will hit the out-breaking routes all day. The “Seam” technique also has implications for how and when defenders will switch off certain receivers, but, just like a matchup zone in basketball, more important than the scheme is the communication and discipline used to make it go.

The upshot of pattern-match zone blitzes is that when executed correctly, they are the best of all possible worlds: They’re attacking, multi-defender blitzes in which the defense plays zone coverage against pass patterns designed to beat man-to-man coverage against pass patterns — all verticals — designed to defeat zones.

The pattern-match zone blitz is not a magic bullet that solves any problem dynamic modern offenses might present. Every scheme has its strengths and weaknesses, and it’s still up to the players to bring the diagrams to life. But blitzing is as old as football itself, and as long as Rodgers, Brady, and Manning are playing quarterback, to blitz, teams must cover as well.

More than a decade after their meeting in Baton Rouge, Arnsparger, another Super Bowl appearance under his belt and now retired, visited LeBeau at the Bengals training camp in Georgetown, Kentucky. “I watched a practice, and afterward Dick and I chatted. I thanked him for his kindness and congratulated him on developing the zone blitz to the point where it is today,” Arnsparger writes. “The scheme has grown a great deal since the beginning. Like everything in football, when you see something good, you add your ideas and make it better — and the zone blitz is no exception.” Great coaches do not necessarily seek to fundamentally change the game, but instead are stewards for a time — for their players, for the ideas of the day, for football itself — merely doing their best to leave each better than they found it.