It is the Broncos’ “Bear” call. Sylvester Williams, a hulking, 313-pound nose tackle, the largest player on Denver’s defensive line, a guy who gets paid to get in the way, drops into pass coverage.

“That ain’t normal,” Williams said. “But that’s one of my favorite plays.”

His job on this play is to keep a running back from catching the ball. No defense ever asks a nose tackle to play like a cornerback. The Broncos are not like everyone else.

“We’re different — a lot different,” he said.

When the Denver defense lines up next month to open the season in a rematch against Carolina quarterback Cam Newton and the Panthers, it will be trying to duplicate one of the most impressive playoff showings of all time, capped by a brilliant Super Bowl. In that game, Denver sacked Newton six times, intercepted one of his passes, scored a touchdown and nearly scored another. It put that defense in a discussion among the great defenses of the past 30 years.

But the league does not quite know what it sees in the Denver D. The Broncos are an outlier in the staid NFL. They confuse fans and hardcore insiders. With defensive coordinator Wade Phillips, a football lifer who learned from his dad, Bum, the Broncos are conservative radicals, a stick-to-basics defense that bucks the trend of complicated schemes in favor of beautiful simplicity.

The best defense in the NFL plays in plain sight. And nobody can pin it down.

“They say they know what we’re going to do,” Phillips said, “but can they stop us?”

“JUST GO PLAY”

To borrow a board game tagline, the Broncos’ defense takes a minute to learn and a lifetime to master. Bum Phillips upset the defensive order in the 1950s when he was coaching small town high school football in East Texas. He developed a way to number defensive lineman to make it easy for kids to know their roles. And he introduced a 3-4 defense — three linemen up front, four linebackers in the middle. His ideas trickled up the ladder.

Paul “Bear” Bryant borrowed Bum’s ideas at Texas A&M in the late ’50s. The NFL, with many teams still using five-man fronts built to stop the run and ignore the pass, soon followed. And the 3-4 defense began to take hold.

Wade Phillips, who also came up through the Texas high school ranks, spun the 3-4 even further. He recognized that the 3-4 can be the most adaptable defense in football. It’s built to let players do what they can do best. If a linebacker is good at coverage, let him cover. If a cornerback can rush the passer, cut him loose. And if a 313-pound nose tackle is quick enough to chase a running back, go for it.

“That’s our philosophy. Just do what the guy can do,” Phillips said. “I can think of a lot of different defenses. But it’s about what the players can do. I’ve always thought that way. When I coached in high school, some guys can’t play very well at all and you have to get by with what they can do. Maybe I got that from my dad. But when I started coaching, it just made sense to me that way.”

But the Broncos can play very well. They can do just about everything. So the simple structure of the 3-4 allows them to be unpredictable. Positions and roles are only words for roster sheets. In theory, the Xs and Os are starting points. In practice, players play everywhere.

“It is simple. That’s Wade’s goal. It allows you to just play,” Broncos cornerback Bradley Roby said. “The best defenses that I’ve seen, and the research that I’ve done, the common thing I get is they’re simple. Everybody knows their job, everybody knows their adjustments and everybody plays together. Wade’s defense, being simple, it allows our athletes to just go play.”

PLAYING TAG TEAM

This moldability allowed the Denver defense to baffle offenses last season. After the Broncos held Cincinnati to 200 yards passing in an overtime victory in late December, the Bengals’ receivers could not agree on what defeated them. The Broncos played a zone defense. No, it was man-to-man. No, they switched at halftime. No one seemed sure.

The truth is between the lines. Bill Green, a legend in Indiana high school basketball, developed a hybrid defense in the late 1960s and ’70s, that starts as a zone and morphs into man-to-man. Instead of defending one-on-one everywhere, a player defends face-to-face in his area, then withdraws if that player crosses a boundary.

Phillips loves this idea. If Broncos cornerback Chris Harris starts on the right side covering A.J. Green, for example, he can follow him around like a jacket until Green wanders too far, then Aqib Talib takes over.

“We play a matchup zone,” Phillips said, not afraid to reveal his playbook. “It looks like man until you pass him off to somebody else. We started it from basketball, way, way back. Everybody was playing 2-1-2 zone and if the ball went to one side, they stayed in place. But then later on they started moving over. We thought, “Well, we can do that. We’ve got five receivers going out, that’s the same concept as basketball.’ ”

The Broncos’ defense is a tag-team. It plays one-on-one until it decides to play two-on-one. This helped them hold opponents to the fewest yards and the fourth fewest points in the NFL last season.

“It’s simple, but it’s not easy,” Roby said. “There’s a lot of pressure. The heat is on. But that pressure is what makes us work at our best. We’re used to being in man coverage when the game is on the line. When I was younger, in college, any time I’d get a man call, I’d be nervous. But not now.

“In the end, it’s a one-on-one league. As a defense, we win those battles the majority of the time. If it’s a left tackle one-on-one with Von Miller, he’s winning that in two seconds. Teams have to catch us slipping, really.”

Even longtime veterans of the game get confused by Denver’s defense. During the Broncos’ first preseason game, at Chicago, former safety and now broadcaster John Lynch commented about how aggressive Denver was blitzing the quarterback. This set off a battle of semantics after the game.

Phillips retorted on Twitter, saying the Broncos never blitzed. They rushed four defenders, sometimes five, but they never blitzed. A rush is not a blitz. When a defense blitzes the quarterback, they are sacrificing numbers in the secondary in order to add an advantage at the line of scrimmage. It’s a gamble.

“The true meaning of a blitz in football is six guys are rushing and five guys are covering five receivers,” Phillips said. “If a backer or a safety gets a sack, they usually say it’s a blitz. And there’s nothing wrong with that. But a dog (rush) is five people. And a four-man rush or a three-man rush is different.”

Under Phillips, the Broncos rarely blitz. They don’t need to. They can send a four-man rush with Williams and defensive end Derek Wolfe and two linebackers, maybe Miller and Brandon Marshall, or two linebackers and two corners, or a corner and a safety with a lineman and a backer. The combinations are endless. It’s all a rush. And the Broncos can just as easily get to the quarterback without gambling on a blitz.

That way, they can keep their numbers advantage in coverage and still pressure the quarterback. Between options A and B, the Broncos choose all of the above.

“It’s simple — get to the ball,” Williams said. “That’s Wade’s No. 1 rule. Get to the ball. At the end of the day, if you get to the ball, you make plays, you do your job.”

Defenses are necessarily reactive. The offense possess the ball. It dictates the terms. It moves first. The Broncos’ defense, though, is impatient. It doesn’t want to wait for the other team to act first. So Denver often makes the first move.

“We’re a play-making defense,” Williams said. “We’re designed to get up the field. We’re not holding up blocks. We’re not two-gap. We’re making plays. I love this defense.”

SIMPLY CRAZY

Phillips, who was out of football and semi-retired in 2014 before he returned to the Broncos, waited a lifetime for a defense to match his philosophy. He was Denver’s defensive coordinator from 1989-92, then head coach in ’93-94. The Broncos reached the Super Bowl once in that span, in 1990, a blowout loss to the 49ers. His defenses were good. But they weren’t great.

This defense is great. The difference now is personnel. The Broncos have one of the best defenders in the league, in Von Miller, and the best cornerbacks, in Roby, Harris and Talib, and they have defensive linemen who can play in pass coverage and linebackers, such as Brandon Marshall, who can cover ground like a sprinter.

And unlike many other teams, the Broncos’ defensive playbook is thin. The scheme is straightforward. Players play. Chase the ball. Get it done. Phillips figured this out over decades. His idea is to turn over the defense to the guys on the field.

“He’s got a lot of swag,” Williams said. “We have very few calls. He says to the defense, ‘Just make plays!’ That’s his mindset. He’ll call the call, then let us play football. It’s a player’s defense.

“Coach Wade is a genius, man. We trust him because he trusts us.”