JACKSONVILLE, Fla. — The Seattle Seahawks didn’t make the playoffs, but their defense did.

The scheme that carried the Seahawks to consecutive Super Bowls (2013-14) has become increasingly popular around the NFL. It helped Atlanta get to the big game last year and was the catalyst for Jacksonville’s stunning turnaround this season. It also got rave reviews down the stretch in Los Angeles and San Francisco.

In a copycat league, this is the one being emulated right now.

And for good reason. The Seahawks rode the scheme to five straight playoff berths between 2012 and 2016, and as more of Pete Carroll’s defensive assistants moved on to become coordinators and head coaches elsewhere, they brought it with them.

Now, it spans coast to coast.

“It really takes on the flavor of the coaches that are doing it, so they have their uniqueness,” Carroll said. “But there are a lot of similarities.”

Similar results, too.

The Jacksonville Jaguars ranked second in the NFL in yards and points allowed this season, relying on their defense to mask offensive deficiencies. The Los Angeles Chargers ranked third in scoring defense, allowing just two opponents to top 21 points in their final 11 games. The Falcons (eighth) and the injury-riddled Seahawks (13th) weren’t far behind. The 49ers finished 25th at 23.9 points a game, but were considerably better over the final five weeks of the regular season. They allowed 19.9 points during a five-game winning streak that included victories against three playoff teams.

Los Angeles Chargers defensive coordinator Gus Bradley, Atlanta defensive coordinator Marquand Manuel, San Francisco defensive coordinator Robert Saleh, Atlanta head coach Dan Quinn and Jacksonville defensive coordinator Todd Wash all spent time in Seattle under Carroll.

Bradley, Manuel, Saleh and Wash were on the same staff in 2012. Former Oakland defensive coordinator Ken Norton also was there and had the Raiders playing the Seattle scheme until he was fired in late November.

“It’s nice,” Carroll said. “I love that the guys are getting the opportunities and they are doing stuff.”

Seattle players don’t seem as ready to credit anyone for doing it as well as they did.

“There is only one Seattle Seahawks,” linebacker Bobby Wagner said.

Maybe so. Seattle allowed the fewest points (14.4) and yards (273.6) in the NFL during the 2013 season and forced a league-high 39 turnovers. The Seahawks emphatically stated their case as a generational defense — right up there with the 1985 Chicago Bears and the 2000 Baltimore Ravens — with a 43-8 drubbing of Denver in the Super Bowl. The Broncos shattered an NFL record with 606 points during the regular season but were overmatched on the NFL’s biggest stage.

That same season, thousands of miles away, Bradley and Wash were building the foundation for Jacksonville’s current defense.

Two years later, Quinn was implementing it in Atlanta with some help from Manuel. Quinn’s offensive coordinator at the time was Kyle Shanahan, who saw the defense every day in practice and knew he wanted it to be part of his rebuild with the 49ers this season. He hired Saleh. And former Jaguars head coach Bradley resurfaced with the Chargers.

“It’s a very sound scheme that starts with stopping the run,” Shanahan said. “It makes you work all the way down the field, so it’s extremely tough to get explosives on. It’s tough to go against. They make you work for everything, and it’s something that you don’t have to reinvent the wheel every week. It’s something that if you just do over and over and over again, it’s hard not to get better at it.”

The premise of the Seattle defense is that it uses an eight-man box to stop the run (one safety positioned close to the line of scrimmage) and a single-high safety who can get sideline to sideline in “cover three” (a three-deep zone in which defensive backs split coverage areas into three sections). Cornerbacks play a lot of aggressive, bump-and-run coverage that works best when the four defensive linemen are pressuring quarterbacks. Linebackers are usually undersized and fast.

It’s a 4-3 base defense that incorporates many elements of the popular 3-4.

“We are all different in our own ways,” Manuel said. “But … just the understanding of methodically making a team have to go 13, 14 plays to score and play with great red-zone defense and understand that taking the ball away is the most important thing. Plays are going to happen that are big, but if you eliminate the ones that you know are about to happen, offenses have to do something else.

“You call plays that guys understand. You can get exotic (and create) paralysis by analysis; guys are overthinking on the field. That’s part of what you see in this defense. I guarantee you in each one of these (Seattle-influenced) defenses, guys are flying around and playing fast because they’re not thinking.”

Regardless of the schematics and subtleties, the common thread is solid — more like star — players.

Seattle has Wagner, cornerback Richard Sherman, free safety Earl Thomas and strong safety Kam Chancellor, among others.

The Chargers boast disruptive pass-rushers Melvin Ingram and Joey Bosa, linebacker Denzel Perryman and cornerback Casey Hayward. They tied for fifth in the NFL with 43 sacks.

The Jaguars had the second-most sacks (55) in the league thanks partly to Pro Bowl defensive linemen Calais Campbell and Malik Jackson and budding star Yannick Ngakoue. Cornerbacks Jalen Ramsey and A.J. Bouye also were the league’s top coverage tandem, and linebackers Myles Jack and Telvin Smith are two of the fastest around.

The Falcons are built around linebackers Vic Beasley and Deion Jones, defensive end Adrian Clayborn, cornerback Robert Alford and safety Keanu Neal.

All of those guys nearly made the playoffs. Los Angeles and Seattle were among the final few teams eliminated from postseason contention Sunday.

The Seahawks are out of the playoffs for the first time since 2011. The Seattle defense, meanwhile, continues its postseason run, albeit in the form of copycats Atlanta and Jacksonville.

“It’s a difficult scheme to go against because it limits you on some of the things you can do. They specifically take certain things away. You just have to be creative and find some of those basic things and be OK with some easy checkdowns and some easy, quick 5-yard completions because that’s what you have a chance for,” Jaguars offensive coordinator Nathaniel Hackett said.

Added 49ers quarterback Jimmy Garoppolo: “A lot of teams are running this defense. It’s become pretty popular in the NFL. That Seattle scheme, it’s a good one.”