Like most histories, the story of football comes in cycles. Through some accidental or desperation-fueled innovation, a particular scheme comes to prominence. Think Bill Walsh stumbling into the West Coast offense because his quarterback had a popcorn arm. As that system takes hold, opponents around the league start devising ways to beat it. Eventually, defensive fads like the Tampa 2 spread through the league, and the entire process starts anew.

“The beauty of our game is that everything comes in circles,” said Packers offensive coordinator Nathaniel Hackett. “ It’s about people adjusting in the offseason, watching tape, and learning how to attack it.”

Every generation, a new schematic empire rises and falls in the NFL. And as the 2021 season begins, it feels as though the age of the Vic Fangio-Brandon Staley defense has arrived.

Vic Fangio has coached in the league for 22 years, and his status as a defensive mastermind — whether as the Bears’ coordinator from 2015-18 or currently as the Broncos’ head coach — is well established.But 38-year-old Brandon Staley’s first season as the Rams’ defensive coordinator last year was nothing short of a revelation. Despite a shortened, pandemic-riddled offseason, the first-time coordinator orchestrated the best scoring defense in football. A former Fangio disciple who served on both the Broncos’ and Bears’ staffs, Staley took foundational principles of those systems, molded them around stars Aaron Donald and Jalen Ramsey, and used a few tweaks to create a defense perfectly suited for the modern NFL.

Offensive coaches around the league have longed talked about Fangio like some sort of football boogeyman — a 60-something, schematic grim reaper in a crewneck sweatshirt. But in Staley, those ideas had a young, charismatic messenger who used them to elevate two of the biggest names in the sport. In the wake of Staley’s success, the levee has broken. Last year, only two teams — the Broncos and the Rams — aligned with two high safeties on close to 80 percent of their plays. Look at any chart conveying defensive structure league-wide, and those two teams were living in their own unique world. This season, that number could easily triple.

As the Chargers’ new head coach, Staley has moved his system about 80 miles down the 405. The Broncos and Rams will carry over the same ideas. Former Rams’ assistant Joe Berry is now the defensive coordinator in Green Bay. Sean Desai is a former Fangio assistant now running the defense in Chicago. The Lions’ new defensive staff has multiple coaches fluent in these ideas.

And that’s before even getting to the inevitable thievery that will happen among teams throughout the league. “After those types of seasons, all types of people call you,” Browns defensive coordinator Joe Woods said of Staley. “Whatever teams play well, in terms of top defenses, teams start copying certain aspects of what they do.”

There’s no way around it: The dawn of the two-high era among NFL defenses is here, and the league’s offensive coaches know it too. They’ve been in the lab all offseason, preparing for the latest trend to spread around the league. The answers they’ve found could come to define this NFL season.

“As you see offenses that are similar to our offense spread around the league, you have to assume that defenses are going to continue to evolve to take away what you do best,” said Browns head coach Kevin Stefanski. “And that’s where we then have to make a decision on what our counterpunch is.”

When Aaron Rodgers talks about the schematic arc of the NFL, he can sound downright wistful. This season will be Rodgers’ 14th as the Packers’ starter, and the reigning MVP has seen various systems of defense come and go.

“I think it goes back to a central theme in the league, and that’s that it’s very cyclical,” Rodgers said. “It’s very trendy.”

In the span of about 5 minutes, Rodgers guides an evocative tour of the league’s defensive evolution. Early in his career, the 3-4 defense had come back into vogue, echoing beliefs from the 1970s NFL. Then Tony Dungy and Lovie Smith helped usher in the Tampa 2 era, as coverage became king. As offenses spread out, defenses were forced to adapt. In the early 2010s, the Seahawks’ brand of Cover 3 started traveling around the league, with Pete Caroll lieutenants like Gus Bradley and Dan Quinn earning head coaching jobs and taking Seattle’s defensive identity with them.

“Some of those guys started branching out a little bit,” Rodgers said. “You started seeing more teams being able to attack those coverages because they’d seen it every day in practice. There had been conversations between coaches. And then they start figuring out what plays give those defenses the most problems.”

Like many offensive-minded people around the league, Rodgers believes that the ideas Staley — and Fangio before him — have brought will represent the next schematic craze. “I think in a pass-happy league, this is the natural progression for defenses,” Rodgers said. “To say, ‘Can you stick to the run game?’ Can you have patience in the run game?’”

To understand how offenses will respond to the inevitable Fangio-Staley clones, it’s important to know what’s made these concepts popular in the first place. As the Seahawks’ single-high, Cover-3 system became all the rage throughout the 2010s, the play-action elements of the Mike Shanahan-Gary Kubiak offense emerged as its natural foil. Staples like Kyle Shanahan’s Burner concept — which paired a vertical corner route with a deep crossing-route situated behind it — were well suited to take advantage of defenses committed to playing with one single high safety and the other rotated into the box. Savvy play-callers like Shanahan and Sean McVay were able to spam defenses with single-high beaters and watch as they reaped the benefits.

Fangio’s method of defense makes life difficult for opponents in several different ways. The first is with the way he attacks their protections with methods that have tormented coaches from the Shanahan-McVay tree. With simulated pressure looks and odd front structures, Fangio and Staley are able to manipulate protection rules and force offenses to keep a back in protection to limit a quarterback’s options.

“As we’ve seen offenses go away from the West Coast offense — which is all about timing, precision, rhythm, spacing — to more scheme-heavy offenses, where it’s a lot of placing guys in spots and letting the system work, quarterbacks are less able to understand protections because they’re just not trained,” Rodgers said.

Mind games upfront may be a subtle annoyance to folks on the inside, but it’s the approach on the back end where Staley has really gotten the world’s attention. The Fangio-Staley defensive system relies on a shell of two high safeties as the foundation of its coverage philosophy. That starting point has multiple benefits for the defense. Because both safeties are playing “from depth,” they’re able to catch all the deep crossing routes that gash defenses content to live in single high. Just as important, a two-high shell also makes defenses much harder to predict. By lining up this way, defenses are able to play any coverage on the menu, and the post-snap picture for quarterbacks starts to blur. Staley’s defense played plenty of Cover 3 last season, but the disguise would often hide the specifics of the coverage until it was too late.

“The two-high and what you run out of that is completely different,” said Lions passing game coordinator Aubrey Pleasant, who served as the Rams’ cornerbacks coach under Staley in 2020. “I just think with the game being spread out, the game being open, not being able to touch defenders, not being able to touch receivers the way you used to in the first five yards, we try to make it a little more cloudy for the quarterback and make him try to figure out post-snap.”

The central tenet of this defensive philosophy is to limit explosive plays, and Staley’s Rams accomplished that better than any defense in the NFL last season. In a league dominated by high-octane passing, this style of defense sends offenses back to the drawing board, forcing them to reevaluate how they want to shape their passing game.

“[Fangio] is one of the more frustrating coordinators to play, because you’re waiting and waiting for an explosive shot, and they don’t ever give them to you,” Bengals offensive coordinator Brian Callahan said. “If you’re a QB that likes to do that, it can be really frustrating. You almost have to change your mindset when you play against those guys.”