RENTON, Wash. -- When Monte Kiffin ran into Lou Holtz this summer, they talked about their 1977 season as coaches at the University of Arkansas. And they reminisced on memories of a wide-eyed, high-energy, 25-year-old graduate assistant named Pete Carroll.

"We interviewed him. He did a good job with myself and Coach Holtz, so we hired him," said Kiffin, who was head coach Lou Holtz's defensive coordinator at the time.

"Then about a month later or so, [Holtz] said, 'Who’s that young guy in the back of the room?' Now, Pete was 25 at the time. He looked like he was 18. I said, ‘Well, that there is Pete Carroll, Coach. We hired him a month or so ago. Get to know him because he won’t be here long.'"

Kiffin was right. Carroll left the next year to coach the secondary at Iowa State. But he and Kiffin would connect at various stops in college and the NFL.

Carroll, whose Seattle Seahawks defenses have allowed the league's fewest points for four straight seasons, is asked often about the roots of his philosophy. And nearly every time, his response mentions Kiffin and the one year in Fayetteville, Arkansas.

"I owe him everything," said Carroll, now the oldest head coach in the NFL at 65. "He taught me everything I know about defense."

The Seahawks have had three different defensive coordinators in the past five years. But their recipe for success has not changed. Heading into Week 9, the Seahawks ranked second in the NFL in points allowed (15.57 points per game) and third in defensive efficiency.

The Seahawks' defense combines talented players with a scheme that fits their strengths. And the principles from 1977 continue to guide them.

Stopping the run

Turn on any pregame show or read a trend piece about the NFL, and you'll almost certainly be reminded of one thing: It's a passing league.

But Carroll believes a defense which struggles to stop the run is a defense that lacks discipline. He prefers speed and athleticism over size and has described the Seahawks' defensive fronts as a 4-3 with 3-4 personnel.

"That really came out of all the way back to Fayetteville," Carroll said. "It was a one-gap principle defense way back then. Monte and I, when we were together in Minnesota with (former Vikings defensive coordinator) Floyd Peters, we were able to continue to build on and NFL-ize our scheme. And so, it’s been a way to get guys to attack and play aggressive so that you can get good pass rush and still fit on the run. That’s where the secondary fits and stuff like that really comes into play."

All coaches seem to agree on the importance of catering scheme to fit personnel, but only the really good ones are flexible enough to follow through.

Carroll believes in one-gap principles where the players attack rather than read and react. But the Seahawks have adjusted their fronts over the years, using two-gap principles at times.

"Probably over the years, I feel like I’ve stayed within the same scheme for all these years, so we’ve done everything you can think of, and we’ve had every type of player you can think of," Carroll said. "And so we have that in our backlog and reservoir of stuff so that we can compensate for special qualities and technique and style of players so that we can utilize them and put them in the best situation for them. We’ve had so much scheme, and we’ve done so many things that we just have a lot of choices, and that’s really helped us out."

The Seahawks rank second against the run and finished in the top three in 2014 and 2015.

Not a traditional Cover 3

While Carroll learned his philosophy from Kiffin, they had different preferences when it came to coverage. Carroll preferred to play with a single deep safety in the middle of the field.

"It’s because of the corner play," Carroll said. "Monte wasn’t as big a corner guy as I am. So I always, at [USC], wanted to be Corner U, or Linebacker U. Because we had a way that we believed in teaching corners that could really play on the line of scrimmage and play really aggressively. We wanted to take advantage of that.

"So when you have that, then you can do other things with your front, and we’ve been able to stay in a heavy, loaded-up front mode for all of these years. So it’s always given us a great chance to play the run. But I do think it’s because of our understanding of how to coach the secondary."

On most early downs, the Seahawks play Cover 3 -- a three-deep zone with four underneath defenders. That allows them to consistently have eight defenders in the box to stop the run.

The curl/flat defenders generally drop to a depth of about 8 yards and a width near where the numbers are painted on the field.

The hook/curl defenders drop 8 to 12 yards at a width of about 1 yard outside each hash. They adjust their depths based on down and distance, along with the drops of the quarterback. For example, if the opposing quarterback takes a three-step drop, the defenders know the ball is going to come out quickly so they don't have to play as deep.

The three deep defenders -- the two outside corners and the free safety -- split the field into thirds.

But the coverage is more complicated than dropping to a spot on the field and waiting for an offensive player to arrive. What has made the Seahawks so good is a concept called pattern-matching or pattern-reading.

Because the Seahawks play so much Cover 3, they see the same route combinations over and over again. Players are taught to read the eyes and shoulders of the quarterback so that they can position themselves properly, break on the football and eliminate yards after the catch.

"It’s just a principle of understanding what the routes are and the combinations that happen and working with guys to their drops accordingly," Carroll said. "We play off of the cues that you get from the offense. So you’re matching up your drops based on what we’re doing."

Linebacker Bobby Wagner most often plays as a hook/curl defender. He played Cover 3 in college but said the Seahawks' version is different.

"It’s more advanced in the sense of route recognition and players," Wagner said. "You have to have a better understanding of route recognition and understanding that as the routes get downfield, you have to match them."

Offenses like to attack both seams vertically against Cover 3 and get a two-on-one situation against free safety Earl Thomas. The hook/curl defenders are often charged with running downfield and covering one of the receivers.

"We prepare for it," cornerback DeShawn Shead said. "We definitely put the hardest combinations and hardest route concepts; we practice against those. We practice against those and get good at it. And the offense tells you everything that they’re going to do, so we’ve got to play smart as well. Formation recognition will tell you when those routes are coming, and so if you recognize the formation, then we can anticipate those routes and we’ll be able to take care of it and eliminate it."

Shead has solidified the Seahawks' right cornerback spot, but he also has experience playing strong safety and free safety.

He explained why the team has rules for the underneath defenders and their drops in coverage.

"Quarterbacks and route concepts end up in those spots, so that’s why those landmarks are there," he said. "Because a lot of concepts, quarterbacks are trying to throw there. And so typically if you’re in your spot and watching the QB, then those concepts, the QB will bring you right to it."

Without proper communication and high-level route recognition, the defense doesn't work.

"The problem is some people, they don’t know how to match the routes," Kiffin said. "But Pete’s scheme, you play zone defense; they’re going to throw seams on you all day long or all-go specials. You better understand how you cover the seams because people spread you out nowadays, and so Pete has a good feel for that. It’s a matchup zone is what it is. It’s not your typical zone."

Limiting explosive plays

It's not unusual during a Seahawks game to see defensive players give one another high fives after a quarterback completes a 6- or 8-yard pass.

Why? Because they don't think most offenses can score a lot of points that way over the course of an entire game. They'll limit yards after the catch and deliver punishing hits. They'll find a way to create turnovers. Or their pass rush will force the quarterback into negative plays.

Even if those things don't happen, forcing the offense to string together long drives will likely keep the game within reach in the fourth quarter. That's why Carroll emphasizes finishing.

The numbers back his philosophy. According to Football Outsiders research, the Seahawks have led or been within one possession in an NFL-record 95 consecutive games. Bottom line: They may lose, but they're not going to get blown out. One reason is because they limit explosive plays.

The No. 1 rule for Seahawks cornerbacks is to stay on top of receivers and play the fade route, using a step-kick technique that requires extreme patience at the line of scrimmage.

Thomas, the free safety, generally lines up 12 to 14 yards off the line of scrimmage and focuses on shutting down posts and seams.

"When you’re playing a single-high defense, that’s where offenses try to attack you," said defensive coordinator Kris Richard. "That’s really what it comes down to. They’re going to try to find as many guys as they can to put into that area."

Once again, the Seahawks have adjusted their scheme to match personnel. Kam Chancellor is mostly used as an underneath defender so he can play the run and deliver big blows on short completions. Thomas most often patrols the deep middle of the field.

"If you go back through the years, [San Francisco 49ers safeties] Merton Hanks and Tim McDonald, totally opposite players," Carroll said. "And Troy Polamalu [played for Carroll at USC] with anybody who could play the middle was unbelievable because he was such a great player close up."

The cornerbacks often press at the line of scrimmage. The Seahawks' defense wants to take away easy throws and disrupt the offense's timing. In basketball terms, they want to take away layups and 3-pointers. If an offense can consistently beat them with mid-range jumpers, they'll live with that.

Teams will often try to take one of the Seahawks' cornerbacks deep and then run a wheel route with a running back behind them. Or the opposing team will try to suck the hook/curl defenders up to the line of scrimmage and attack the seams in front of the free safety.

"It’s a copycat league," Shead said. "So if a team runs a play that’s successful on us, we’re likely to see that same concept the next three to four games until we stop it. And it just goes on and on -- same concepts and everything. It’s Cover 3, single-high safety. And teams have beaters against Cover 3, and they try to attack those weaknesses and those zones."

Like most teams, the Seahawks play a lot of man coverage on third down, and they'll sprinkle in some looks that have two deep safeties.

They're blitzing 29 percent of the time this season (13th most), which is up from previous years. And Richard Sherman is shadowing No. 1 receivers more than ever before.

But at their core, the Seahawks are the same defense they've been since Carroll arrived.

"That’s what we always do," Sherman said. "There’s always a ton of questions going into the week of how we’re going to change and do this. For five, six years now, we’ve answered that question the same exact way by playing the same way we always play. There are times where other teams are trying to figure out what we’re doing like we’ve changed something over the years, like we’ve changed coverages, like we do something exotic. We don’t do anything exotic. We play as hard as we can as long as we can, and we make you deal with us."

Players over scheme

Gus Bradley and Dan Quinn, former Seahawks assistants, have tried to run the Seahawks' scheme as head coaches in Jacksonville and Atlanta, respectively. But their defenses have struggled.

The biggest factor in the discrepancy is talent.

General manager John Schneider and his staff, which includes co-directors of player personnel Scott Fitterer and Trent Kirchner, have done a brilliant job of finding talent that fits Carroll's scheme. Thomas is the only first-round pick among the Seahawks' defensive players.

Thomas, Sherman, Chancellor, Wagner and defensive end Michael Bennett are Pro Bowl players. Linebacker K.J. Wright and defensive end Cliff Avril could receive their first nods this season.

Carroll values athleticism, smarts and instincts. He wants players to know their assignments, but he doesn't want them to play like robots.

"The freedom comes with the discipline, that they learn how to do their job and they understand it so well that they know the primers and boundaries of what they can and can’t do," Carroll said.

"That allows the expression of freedom to come out and the opportunity to improvise to some extent. That comes from discipline and repetition and great practice and great experience. Just think of it as in the world of performance, dancers and musicians get better, they keep playing, and they take themselves into a different realm of freedom and improvisation that allows them to really express what they’re all about. Hopefully, in our world here, that’s what happens."

The foundation of the Seahawks' defense was built on the back end, and with Carroll having signed a contract extension through 2019, the hope is Kiffin's principles will pave the way for another Super Bowl.

"I’ll tell you what Pete Carroll is: He’s a great fundamental coach," Kiffin said. "He just believes in fundamentals. He believes in players playing fast and knowing what they’re doing. To do that, you have to have position coaches on your staff that are great teachers. It doesn’t matter how much you holler or this or that. It’s about being a great teacher. Teach players how to get better, and they’ll play their butt off for you."