Guide to Defenses 2
By Jene Bramel
August 20th, 2010

Part 2: The Evolution of the 4-3 Front

The earliest decades of pro football defensive play saw teams stack the line with nine, seven and six man fronts to stop the run-heavy offenses of their day. As the forward pass gained favor, coaches needed to devise ways to drop more men into coverage, but still stop the ground game.

During the 1940s, Philadelphia coach Greasy Neale's "Eagle" defense was slowing the league's best offenses with a five-man front and four-man secondary that was equally successful against the run and pass. By the end of the decade, Paul Brown and a balanced Cleveland offense that featured a power running game complemented by a precise, athletic passing attack had been scoring at will on the five and six man defensive fronts that then dominated the league. The two juggernauts met in 1950, and Brown destroyed Neale's Eagle defense.

The best defensive minds knew they had to adjust and adjust quickly. They went to the chalkboard, tweaked their current schemes and the 4-3 was born.

Forerunners of the 4-3

To build the 4-3 from the defenses of the 1940s, two major schematic changes had to take place. The first can be credited to Neale, who dropped one of the front eight players in the common 5-3 defenses into the secondary. His Eagle defense was a 5-2-4 alignment and the first defense to regularly use a seven man front and four defensive backs.

Neale's defense was versatile and successful. His talented front five stopped the run, while his two linebackers either smashed the receivers coming off the line or helped to pressure the quarterback. The fourth defensive back allowed Neale to better defend deep routes while the front seven pressured, blitzed and covered. The 5-2-4 ruled the day until Brown made a simple adjustment to his T formation that allowed his high-powered offense to gut the Eagle for 35 points.

Brown split his quick and athletic ends and put pressure on the defensive backfield. When the linebackers cheated outside to help, the Browns widened their offensive line spacing and stretched the Philadelphia front five and then gashed the Eagles with Marion Motley up the middle. The talented players of the Cleveland offense made the blowout win possible, but the blueprint Brown used to beat the Eagle defense was clear for all to see. Spread the field, pressure the flanks with speed and timing passes while attacking the vulnerable middle with the run.

It didn't take Giants' head coach Steve Owen long to scheme a way to stiffen the middle of his defensive front while still pressuring the short passing lanes that Brown favored for his timing routes. Owen's scheme came to be known as the "Umbrella" defense, and it led to the second major schematic change - the four man defensive line - needed to invent the 4-3 front.

But it wasn't Owen who taught the scheme to his teammates. It was his talented young defensive back, Tom Landry.

On paper, the Umbrella was to be a 6-1-4 front at the snap before morphing into something else entirely. In practice, it melded concepts from Owen's preferred 5-3-3 and Neale's Eagle defense. Like the Eagle, the Umbrella featured four defensive backs to counter the Browns' speed and spread formations. Owen kept the middle linebacker from his 5-3-3 to help bolster the middle against the run. What made the Umbrella special, however, was Owen's plan (as taught by Landry) to flex his defensive ends into standup linebackers at the snap and drop them into the short passing lanes.

The wrinkle was hugely successful. In its debut against Cleveland, the Umbrella held the Browns' offense without a pass completion in the first half. There was no room to complete passes against the bracketed coverage of the Giants' defensive backs on top and the flexed defensive ends turned linebackers underneath. The Giants won the game 6-0 by flexing to a four man front with three linebackers and the first 4-3 fronts were about to be born.

As the 1950s wore on, more teams adapted the concepts Owen introduced. Since offenses now knew that his ends would often drop into standup linebacker roles, Owen soon moved them back off the line into full time outside linebackers. Neale dropped his middle guard off the line and changed his Eagle into a variation of the 4-3. The Bears' Bill George and the Giants' Sam Huff became stars at the middle linebacker position.

The Eagle and the Umbrella were the earliest versions of today's 4-3 fronts, but they resemble today's 4-3 fronts in name only. Not surprisingly, it was Landry who developed some of the first innovations in the process, many of which still shape 4-3 fronts five decades later.

Landry's Flex

The earliest 4-3 fronts were symmetrical or "even" fronts, and asked each defensive lineman to align head up on an offensive lineman, with defensive ends lined up over offensive tackles and defensive tackles over offensive guards.

Power running offenses began having success turning the defensive linemen aligned head up at the snap and opening rushing lanes. Giving the offensive lineman the option to block their defender in either direction gave a running back the option to wait until a hole appeared before committing. Though the 4-3 defense had further established itself behind talented groups like the Fearsome Foursome and the Purple People Eaters, option blocking and the "Run to Daylight" concept was testing the limits of the 4-3 by the mid to late 1960s.

Landry's Flex defense was the answer. Fans of pro football history probably remember the Flex for its unusual defensive line alignment, which "flexed" two defensive linemen - usually one tackle and one end - a few feet off the line of scrimmage. However, the flex itself isn't the innovation that's stood the test of time. Two other concepts critical to the success of Landry's defense are still important parts of 4-3 defensive play today.

First, Landry shifted his line so that they were no longer aligned head up on an offensive lineman. He asked each lineman to play a single gap to make them more difficult to option block. Next, Landry asked them to sit in those gaps and control the area they were assigned, reacting only when the ball came to their gap. Though the middle linebacker was responsible for two gaps, the three linebackers were asked to do the same. The unusual decision to flex two linemen off the line of scrimmage further stymied the option blocking process and allowed the defenders to see the flow of the play before attacking but it wasn't absolutely necessary to the success of the scheme. And the scheme was successful.

The one gap design and the read-and-react philosophy not only slowed "Run to Daylight," they remain core concepts in many of today's 4-3 defenses.

Stram's Odd Front

About the same time Landry was tinkering with his 4-3 in Dallas, defensive coaches in the AFL were also making changes to the alignment of their front four. Whether it to create mismatches by putting a bigger defensive lineman over an undersized center or to move more defensive players toward the likely point of the offensive attack, the defensive lines were shifting. Instead of aligning symmetrically in the even formation, a few defenses in the AFL began to move one defensive tackle over to align helmet to helmet on the center in what came to be called an "odd" front.

(Calling a 4-3 front an "odd" front is a little confusing. 3-4 fronts with a nose tackle head up on a center may also be called odd fronts. If you're a stickler for terminology, it's probably considered correct to call any front with a defensive linemen head up on the center an odd front.)

The odd front 4-3 could be shifted toward or away from the strength of the offense. Though others used it before him and there were other innovations (e.g. the stacked linebackers) that helped contribute to its success in Kansas City, the odd front innovation is often associated with Hank Stram's defenses of the early 1970s. With huge defensive tackles Buck Buchanan and Curley Culp dominating overmatched centers, the Chiefs' talented group of linebackers was free to make plays all over the field.

The shifted fronts were the precursor to the over (tackle shifted toward offensive strength) and under (tackle shifted away from offensive strength) fronts discussed in the first installment in this series. Floyd Peters, Joe Collier, Bum Phillips, Monte Kiffin and Tony Dungy, among others, have all made them integral parts of their successful defenses, both 4-3 and 3-4.

The 4-3 front continued to have success in the 1970s, but the league began to trend toward the new 3-4 front to keep offenses from outflanking their three linebackers with bigger and faster running backs and a variety of new passing attacks. By the mid-1980s, the majority of NFL defenses had switched to the 3-4.

Around that time, however, a 4-3 revolution of sorts was happening in the college ranks. Simplicity was key. Size no longer mattered. Speed and aggressiveness ruled the day. The new, "college" 4-3 was winning multiple national titles. Eventually, it would begin winning Super Bowls.

The Miami 4-3

It might be a stretch to call Jimmy Johnson the lone driving force of the move back to the 4-3 front in the 1990s, in the college or professional ranks. But the attacking style of defense he brought to the NFL from his days as a college coach is called the "Miami" front by many, and continues to impact the league today.

Johnson knew he couldn't recruit successfully against the big schools in his first head coaching gig at Oklahoma State. So he focused on recruiting athletes. Football talent and size was nice, but he made speed and athleticism his priority. He simplified the 4-3 scheme to a bare bones approach. There would be no reading and reacting, no camping in a specific area and controlling your gap. Instead, he coached his players to attack, penetrate and swarm along the front seven and used simple zone coverage in the secondary. He took safeties and made them linebackers. He turned linebackers into speedy, edge rushing defensive ends. Within ten years, a huge number of college coaches had followed suit. In time, those coaches began producing a new class or defender that would change the face of defensive football in the NFL.

Though the philosophy of the defense was the major difference from earlier 4-3 fronts, there were also a couple of minor schematic differences. His SLB usually aligned off the line, while his speedy defensive ends lined up a little wider than the previous generations of the 4-3.

The alignment itself wasn't groundbreaking. Rather, it was the attitude and team defensive speed that drove the scheme's success.

Johnson wanted his athletic defenders exploding off the ball into their gaps. He had his front four crowd the neutral zone as much as possible without drawing penalties. The linemen were to make the offense react to them while they "read on the run" rather than simply controlling their gap then reading keys to decide what to do next. The wide alignment of the ends allowed them to get upfield quickly to get to the quarterback or disrupt a running play in the backfield. If they weren't successful, they often forced the play back to the MLB shooting his gap or pushed the play out to the pursuit, where an OLB shooting his gap could make the play. Those smaller, speedier linebackers would theoretically be protected by a couple of massive, but still quick defensive tackles that were disruptive enough to keep the linebackers (and the MLB in particular) clean to stop the run and create negative plays. The edge rushing line and swarming Cover-2 shell was designed to create turnovers against the pass.

The last two sentences hold the key to Johnson's philosophy. The aggressive nature of this 4-3 front might allow big plays at times, but the negative plays and turnovers gave the ball back to the offense quickly and with good field position if the defense itself didn't score. It worked.

As Johnson's scheme succeeded, he was able to recruit better and better athletes and eventually work his way to the NFL. As so often happens, copycat programs in college churned out players who fit the scheme of the day and pro teams looking to piggyback on the success of Johnson's Cowboys incorporated those players into the "Miami" scheme. The NFL became a 4-3 league again.

The Miami 4-3 has holes. The smaller ends and OLBs can be exploited by a good rush offense. Overpursuit can be an issue. Zone coverage becomes a problem if you don't have the athletes to rush the passer. As we'll see with the Tampa-2 and the 3-4 in later installments, finding the right players to run such an aggressive scheme is difficult when everyone's running the same defense and searching for the same type of player. Among other issues, those deficiencies partly account for why Johnson's assistants never amounted to much as head coaches.

Still, the era of undersized defensive players succeeding in 4-3 fronts is still going strong and its legacy is directly traceable to the success of Jimmy Johnson and the "Miami" 4-3.

Contemporary 4-3 fronts

Most 4-3 defenses today use either the read-and-react philosophy of the Landry flex or the read on the run philosophy of an aggressive, downhill front like the Miami front (or a variation of Buddy Ryan's aggressive 46 defense). Some may use a little of both depending on personnel. Almost all have playbooks that include over and under fronts.

But the evolution of the 4-3 didn't stop with Jimmy Johnson's aggressive use of undersized, but quick talent. The past decade saw the introduction and widespread use of a variation in coverage known as the Tampa-2 and a hybrid defense that combines both 3-4 and 4-3 concepts to highlight a roving pass rusher as the centerpiece of an aggressive front seven. In the next installment, we'll look at those variations and wrap up our look at the 4-3 front.


Knowing which type of 4-3 a particular defensive coordinator prefers to run can be an important clue to the potential fantasy value of a given linebacker. The strongest recent example remains D.J. Williams in 2007.

Prior to 2007, Williams was a base defensive SLB with questionable instincts and the Denver MLB (Al Wilson) hadn't been a premier fantasy option. Enter Jim Bates and his variation on the Miami 4-3 that funnels plays to the MLB and Williams' relative lack of instincts and the recent trend of so-so Denver MLB production were quickly forgotten. Williams finished with 106 solos, 35 assists and a top five fantasy year. Those who had the confidence to rank Williams in the top ten before the season started did so largely on the strength of the potential within his new scheme.

The NFL cycles through defensive trends quickly and with Jim Bates out of the coaching ranks and the Jaguars and Panthers changing 4-3 philosophies in recent years away from a Miami-like front, opportunities to exploit variations in the 4-3 when ranking middle linebackers have mostly dried up.

While the Miami front has cycled out of the league over the past decade, the number of 4-3 defenses using over and under front principles has increased dramatically. The alignments and philosophies of the under/over 4-3 fronts provide similar opportunities for watchful IDP owners, however, and we'll take a closer look at those after our next installment.

Questions, suggestions and comments are always welcome to

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