MIAMI — One Sunday this past December, Tyrann Mathieu marked his exalted place in the NFL, a status he had labored years to reach, with an unspoken declaration. He sniffed out a New England Patriots’ screen pass, sprinted to the receiver as if propelled by jet fuel and pummeled the ball carrier. He hopped to his feet, glared at the brainiest sideline in football and tapped his helmet three times. It was his message to New England’s offensive coaches and maybe an affirmation to himself: “I’m too smart,” Mathieu said. “I’m way too smart.”

For the remainder of the season, teammates took up the celebration as a rallying cry. Special teams ace Daniel Sorensen pointed to his head after he spoiled a fake punt. Defensive end Frank Clark looks for opportunities to draw attention to his brain. They are following Mathieu’s lead.

“He lets you know he knows exactly what you’re doing,” Clark said. “That’s been our philosophy: You can game plan all you want. At the end of the day, we’re going to game plan a little bit harder.”

A defense that smothers opponents with smarts and brawn, that plays with swagger, that’s good and isn’t afraid to say so: These are the Kansas City Chiefs we’re talking about? Yes. The Chiefs changed everything on defense this offseason, an organizational overhaul that included a new coordinator (Steve Spagnuolo), a new scheme (from 3-4 to 4-3) and the importing of a passel of new players in trades (Clark), free agency (Mathieu, Alex Okafor) and the draft (injured safety Juan Thornhill, defensive tackle Khalen Saunders).

For all the new plans and pieces, Kansas City’s defensive transformation began with the player teammates still love to call the Honey Badger. Mathieu is a storm of calculated mayhem, a worker bee who wakes up at 5:45 each morning and a heat-seeking missile who can line up or strike from anywhere on the field. He has changed the Chiefs in elemental ways with his all-pro performance and his mere presence.

“He’s a special person,” Chiefs General Manager Brett Veach said. “It’s really hard to explain the power someone like that has unless you’re actually in the building. . . . You have to get talent. You have to build a deep roster. You need corners, and you need rushers. Until you get a catalyst, it’s hard. You need that one guy that will make everything go. He’s certainly that guy. To have him on our team has meant everything to us.”

The Chiefs are in the Super Bowl primarily because their offense consists of Patrick Mahomes at quarterback and a receiving corps that would strike fear in an Olympic relay team. But they had the same components last season and fell a game short. Their defensive leap forward explains their AFC title just as well.

In 2018, the Chiefs finished 31st in yards allowed and 24th in points. With their season on the line in the AFC championship game, the Chiefs yielded an overtime touchdown drive to the Patriots on which they allowed two backbreaking third-and-long conversions. This year, they improved to 17th and seventh, and in their past eight games, playoffs included, the Chiefs allowed an average of 15.5 points.

“I think one guy can have an effect on every other guy,” Spagnuolo said. “When they start to elevate what they’re doing, it just permeates. It starts like a ripple effect — you throw the stone in the pond. I think Tyrann has that effect.”

Mathieu is 27 years old, but he has graduated to the level of sage in seven seasons. Mathieu carries himself with openness and contentment, and it gives him the air of someone much older. His travails somehow transcend normal age perception. Linebacker Anthony Hitchens is also 27, and he reminisced about watching Mathieu play at LSU.

“As a kid, you watch him,” said Chiefs safety Jordan Lucas, who is one year younger than Mathieu. “I used to watch his highlight tapes. Just seeing him in person and seeing how it translates to the field, it’s crazy.”

Mathieu traveled a crooked path to wizened team leader. He grew up with an absent mother and a father imprisoned for murder. He was a Heisman Trophy candidate as an LSU sophomore, but drug use cost him his final college season and caused his plummet to the third round on draft day.

Mathieu went through rehab and established himself by making the all-rookie team, but in the final game of his first NFL season, he tore his left ACL returning a punt. He missed much of 2016 because of a shoulder injury, and after 2017, the Cardinals cut him after he refused a pay cut. He starred for the Texans last year, and he signed a three-year, $42 million contract with the Chiefs.

The experiences — and how he transcended them — gave him credibility in NFL locker rooms. His serious, studious approach to football earned him authority. His story and the way he seized control of it are his currency.

“I regret what I’ve been through,” Mathieu said. “But it made me who I am today.”

Through contacts in the league, Chiefs front-office personnel learned Mathieu could have a profound impact on a locker room. They heard he had rivaled J.J. Watt’s leadership in Houston. At the outset of the offseason, they made him a priority.

“We didn’t pull names out of a hat or throw darts at the board,” Veach said. “We really wanted to get the Honey Badger here. We thought his leadership and presence on the back end would be something that would be infectious from top to bottom.”

Teammates voted Mathieu a captain, a designation earned through diligence. Mathieu arrives at Kansas City’s facility before most teammates and leaves late. If he makes a mistake in practice, he asks coaches to run the play again.

The work allows Spagnoulo to wield him in unusual ways. Mathieu often plays close to the line of scrimmage, which enables him to help defend running plays and makes him a threat to blitz. His instincts and athleticism still allow him to skitter to any coverage assignment. Even as he diagnoses an offense’s intention with care, he plays with fury.

“I joke with people that we have this key and this cage, and we just unlock the cage and let the Badger out, man,” Coach Andy Reid said.

In Week 13 against the Raiders, Mathieu was assigned to cover wide receiver Tyrell Williams in the slot. As Williams sprinted down the field, Mathieu read quarterback Derek Carr and diagnosed the route combination. He abandoned Williams just before Carr threw and cut in front of tight end Darren Waller to intercept the pass. How could he have been so certain where the ball was going?

“I don’t know,” Sorensen said. “Maybe he’s got a sixth sense. It’s just vision, right? You can only react to things that you can see. He has the ability to open up his vision and see everything. He can see the whole field and see how the concepts are coming to him, and he’s able to process all of that.”

Mathieu credited his football sense to coaching. His high school defensive backs coach, Del Lee, was both his father figure and football elder. Lee taught Mathieu precise technique, the importance of playing with leverage and the way to read a quarterback’s eyes.

“A lot of this stuff I’ve seen before,” Mathieu said. “In my sleep. I’ve seen it in the game. Maybe I’ve seen it in a daydream. I just see certain plays all day.”

Through his will, Mathieu has transferred some of that vision to his teammates. They relish the head point Mathieu turned into a motto. They have learned it is impossible to play football with Mathieu and not feel his presence, and that mostly translates to joy.

“People love to say, ‘I made that play,’ ” Mathieu said. “‘I guess I am kind of smart.’”