This is Part 1 of our series “After the Boom,” examining how NFL defenses should adjust to modern offensive schemes that have made the game far more complicated. Part 2 examines current pass defense concepts and how they need to change. Part 3 explores new defensive line techniques that should migrate to the NFL. Part 4 details how NFL teams should go about building a roster fit to play a more modern scheme.

Punch. Counterpunch.

That might be the best way to describe the schematic evolution of football. Typically, it’s the offense out in front. The guys with the ball present a new concept or system that puts defenses at a disadvantage; other offenses follow suit as defensive coaches scramble to find answers. They invariably do and force another adjustment from offensive coaches.

The fight never ends. It just gets more complicated.

In 2019, NFL defenses — having claimed a small victory during the 2017 season, when the scoring average dropped to 21.7 per game and inspired countless What’s wrong with NFL offenses? think pieces — are once again on their heels. With more NFL coaches fully embracing the once-frowned-upon concepts that have dominated college football over the last decade, pro defensive coaches — who’ve had it far easier than their peers at the lower levels thanks to the homogenous nature of NFL offenses — have to get craftier than they ever had in order to keep up.

What’s next for NFL defenses?

There’s been plenty of talk this offseason about the coming offensive revolution, in part because the No. 1 draft pick was a dynamic QB who has been paired with a head coach who is so offensively innovative that he got hired in Arizona even after not winning enough to keep his job at Texas Tech.

I broke down the ramifications of the Kyler Murray and Kliff Kingsbury pairing months ago. And then I got to thinking: What must defensive coordinators be thinking? And where will they look for answers?

So I set out to find out.

Finding the real innovators

For whatever reason, schematic innovation tends to trickle up in football. It’s the high school and college coaches doing most of the innovating, and, eventually, those new concepts make their way into the NFL.

Take the read option, for instance. While the Falcons experimented with using Michael Vick on designed runs, those concepts did not become a staple for NFL offenses until 2012 when Cam Newton, Robert Griffin III, Colin Kaepernick and Russell Wilson forced defenses to account for an 11th man in the run game for the first time ever. Well, college teams had been running the zone read for over a decade by that point, and college defensive coaches had already developed answers to combat the scheme. Defensive coaches at the highest level of the sport, who are very much isolated from their peers at the lower levels, were forced to scramble for answers.

So I went looking for the coaches who’ve already dealt with all the things Kingsbury and a new generation of offensive coaches will bring to the NFL. Cody Alexander, a high school defensive backs coach in Texas who runs the excellent Match Quarters blog and has written two books on modern defense, remembers visiting the Broncos in 2013 and talking to Jack Del Rio and John Fox about Robert Griffin III, who was with Washington at the time. He told Touchdown Wire’s Doug Farrar:

“And they were wondering, what are we going to do about the zone read? And I’m thinking to myself, this is like Day 1 install — these are simple option rules. I think there’s a little bit of a disconnect with some of the older NFL establishment, especially on the defensive side.”

While Fox, Del Rio and other members of the NFL’s old guard were looking for answers, a defensive coach who had spent the previous decade dominating college offenses was using some of what he learned at USC to build a dominant defense in Seattle. Pete Carroll’s Seahawks were throttling NFL offenses thanks to his simplistic scheme that limited the thinking his players had to do. Seattle rarely, if ever, came out of their single-high coverage shell. Coverages fall into two main families: Single-high and double-high. The former has one safety manning the deep middle with the other safety closer to the line of scrimmage; the latter has two safeties deep, essentially splitting the deep part of the field in two. Seattle’s success would change the way many coaches in the league thought about defense — and also help precipitate the offensive evolution that is forcing defenses to change again.

How we got to where we are today

With a free safety like Earl Thomas in the deep middle, Carroll could feel safe bringing his other safety, the intimidating Kam Chancellor, into the box where he, along with athletic linebackers Bobby Wagner and K.J. Wright, could patrol the underneath areas that had been under attack since the NFL employed rules that limited the physical play of pass defenses.

With the NFL rule changes favoring the offenses, dinking and dunking down the field became a viable option, and with offenses putting more receivers on the field, defenses needed more athleticism in those short-to-intermediate areas. The Seahawks had it to spare.

After Seattle won a Super Bowl on the back of its top-ranked defense, nicknamed the Legion of Boom, the NFL lived up to its reputation as a “copycat league,” as teams tried desperately to ape the Seahawks system. They hired Seattle assistants away. They went searching for centerfield safeties who could do what Thomas did for Carroll’s secondary. They looked for long corners like Richard Sherman, who could play at the line of scrimmage and carry receivers vertically downfield. They looked for fast linebackers who could cover and plug gaps in the run game. That Seattle had built its defense with late-round picks may have convinced teams they, too, could find their own Legion of Boom without much of an investment.

The teams running the Carroll system soon found out that it wasn’t so easy. Gus Bradley’s tenure in Jacksonville was a disaster of historic proportions. Dan Quinn’s defense has held back the Falcons throughout his stint as head coach. Robert Saleh has overseen one of the worst defenses in the league these past two seasons in San Francisco. As great as Carroll’s system was for players, it really only worked if those players were exceptionally talented. Matt Bowen, a former NFL safety who works as an analyst for ESPN and coaches high school football, explained to For The Win:

“Look at the Seattle roster that won the Super Bowl. They had the key personnel to [play a simple scheme.] You think about the Bears when Lovie Smith was there, they were playing Cover 2, but they had the front four with two edge rusher who could get home, the disruptive 3-technique in Tommie Harris, Brian Urlacher running the seams, Mike Brown at safety and Lance Briggs at linebacker. They had the key parts to do it. “To play a Cover 3 scheme [like Seattle], you have to have linebackers who can run sideline to sideline and carry, for example, a Tyler Lockett on a deep over route. You have to have corners who are physical and can play vertical match technique outside and get their hands on receivers. And you have to have a gatekeeper in the post, like Earl Thomas, who can shut down the middle of the field. That’s in addition to the front four guys who can rush the quarterback.”

Despite the Carroll tree’s lack of success, single-high coverages — specifically Cover 1 (man coverage with one safety patrolling the deep middle) and Cover 3 (a zone defense with three defenders deep and four underneath) — have become the base call for an overwhelming majority of teams. Per Sports Info Solutions’ charting, Cover 1 and Cover 3 combined for 52% of passing snaps during the 2018 season. Double-high coverages — Cover 2, Tampa 2, Quarters, Cover 6, etc. — were played on only 30.8% of passing snaps.

Seattle’s success wasn’t the only factor contributing to this schematic shift. The new CBA, which limited practice time also necessitated a more remedial approach to defense, Bowen theorized:

“Part of it is that you have limitations in the offseason programs. When I was in the league, the offseason program was like the Wild West. It was almost full contact, even in just helmets. There were no limitations to how much we could be on the practice field, so there was much more time to teach, so you could be a little more complex with the defense.” “When I played under Gregg Williams [in Washington], that was more of a complex defense. Every time someone moved we moved. You don’t have the time to coordinate that anymore. The league is becoming more about alignment and assignment in the fact that you have a short amount of time to work. You don’t have two-a-days. You don’t play much in the preseason anymore. What can I teach in that time? What can I teach rookies in that given amount of time? So I think that’s why you’re seeing more Cover 3 now. It’s easier to teach, it’s easier to install and you don’t have to think as much.”

Offenses begin to adjust

As NFL defenses have called more single-high coverages, NFL offenses have grown more efficient at attacking them. Their weapon of choice has been the seam route. The offense will send two receivers up the seam and force the free safety into a two-on-one that only aliens like Earl Thomas have a chance at defending — especially if those players are getting free releases into the seams, which is nearly impossible to prevent with the league’s rulebook prohibiting even breathing on a receiver. Here’s a young, bespectacled Nick Saban saying as much at a coaches clinic in the 1990s…

“If you have a middle of the field safety in here,” Saban said, “and you let people run down [the seam] — especially if it’s a double seam pass — your middle of the field safety will not make those plays in practice if you do a break on the ball drill with him. He won’t do it — unless he’s a great one. And he probably won’t do it then if the quarterback is a great one.”

Here’s what Saban is talking about. The Saints’ deep safety has no chance: He reads the quarterback’s eyes and drifts to his right to help on the seam route to that side, but that leaves Greg Olsen with a favorable matchup in the left seam.

Saban was talking to a bunch of high school coaches when he dropped that gem but it’s certainly applicable to the pro game, where all of the quarterbacks can make those throws with relative ease. The numbers back that up. Sarah Malle, who was recently hired to the Ravens’ analytics department along with several other analysts who were posting their statistical work on Twitter, used Next Gen Stats data to produce a heat map showing how much success NFL offenses were having when attacking the seams.

Very cool. The blue area shows the peaks along the seams which are the deepest and most valuable areas of the field to attack and still have good chance for a completion. https://t.co/3MEmzzPmk2 pic.twitter.com/pDnt8zSmNs — Josh Hermsmeyer (@friscojosh) June 12, 2019

Not only have teams been completing seam passes at a high rate, but those throws have led to points. On throws to receivers running routes into the seam area — targeted between 10 and 25 yards downfield — NFL quarterbacks averaged 0.46 Expected Points Added per attempt in 2018. Some context: Patrick Mahomes, the league MVP, averaged 0.33 Expected Points Added per attempt. Those open seams can make any quarterback perform like an MVP.

The EPA numbers on those throws against double-high coverages are just as good as they are against single-high coverages, but they happen at a much lower rate. If NFL defenses want to stop quarterbacks from making those ultra-productive throws, they should probably be playing more double-high looks.

Accounting for the QB

But playing more two-deep coverages would require taking a safety out of the box, which would, in theory, give the offense a numbers advantage in the run game. With offenses using the QB run game and RPOs to manipulate those numbers already, defensive coaches have been reluctant to cede the fight for a numbers advantage — hence the league’s predilection for single-high coverages, which allow them to get an extra man in the box. So, defenses that are able to defend the run without committing numbers to the box will be better equipped to stop modern offensive attacks, which revolve around the passing game.

“Most of the teams stop the run with numbers,” says Cardinals defensive coordinator Vance Joseph, who produced one of the more impressive gameplans against the Chiefs last season during his time as Denver’s head coach. “So to play single high and to play [Cover 1], you’ve got to have corners. But the best defenses, honestly, stop the run with shell defense. If you can play a coverage-friendly defense and still stop the run with a six or a seven-man box, that’s genius.”

The NFL’s dedication to stopping the run can also lead to matchups problems for the defense. NFL defenses will typically “match personnel.” If the offense takes a tight end or running back off the field for a third receiver, the defense will typically follow suit and replace a linebacker with an extra defensive back. But, for the most part, defensive coaches are still treating tight ends like block-first players and running backs as non-receiving threats, which allows offenses to easily create mismatches in their favor. In 2018, defenses matched 12 (1 RB, 2 TE, 2 WR) personnel with base defense (four defensive backs) 61% of the time, and offenses produced a DVOA of 3.1%, according to Football Outsiders. When the defenses treated one of those tight ends like a receiver and matched with a nickel defense, their DVOA dropped to -5.3%. It’s time for coaches to re-assesses their notion of what “base” defense should be.

Figuring out what comes next (or at least should)

As NFL offenses continue to evolve and adopt more spread concepts from the lower levels of the sport — and that evolution will only accelerate if Kliff Kingsbury finds any success in Arizona — pro defenses MUST adjust if they’re going to catch up and land a counter to the barrage of punches they’ve taken over the last decade.

How will defenses close the gap? That’s the overarching question I’ve attempted to answer in this series — which we’re calling After the Boom — taking a peek into the future of NFL defense using both statistics and X’s and O’s as a guide.

In Part 2, I’ll be looking at how teams should adjust their preferred coverages in order to best stop NFL passing attacks.

Part 3 will decipher how to teams could adjust their front alignments in order to lean more toward defending the pass while not making themselves vulnerable against the run.

Finally, I’ll cover the roster-building ramifications of this defensive evolution.

By the end, you should have a good idea where defensive football at the NFL level is headed in the next few years.