Jim Johnson teamed with Andy Reid to build a formidable defense in Philadelphia.

To understand Sean McDermott's approach to coaching defense, you have to go back to his formative years at the elbow of his legendary mentor, the late Jim Johnson.

McDermott learned all of the intricacies of Johnson's inventive 4-3 scheme that did plenty to allow the Philadelphia Eagles to become a consistent Super Bowl contender during Johnson's 10 seasons as their defensive coordinator (1999-2008).

McDermott, 42, has carried those lessons with him through a career in which he established himself as top-notch defensive coordinator for the Carolina Panthers, providing the stepping stone to his next job: head coach of the Buffalo Bills.

Johnson's highly impressive résumé included leading a defense that forced an NFL-best 46 turnovers (including a team-record five interceptions returned for touchdowns) in 1999 and became only the fourth in NFL history to go 16 games without allowing more than 21 points. A staggering 26 Pro Bowlers came out of his system in Philadelphia, including cornerback Troy Vincent, linebacker Jeremiah Trotter, and defensive end Hugh Douglas. Johnson also had a major influence on the careers of prominent head coaches, such as Baltimore's John Harbaugh and Carolina's Ron Rivera.

McDermott also joined the Eagles in 1999, as a scouting administrative coordinator. He would become assistant head coach to Andy Reid in 2001, and in 2002, he joined Johnson's staff. For the next eight seasons, he would soak in massive amounts of knowledge in a variety of capacities -- defensive assistant/quality control, assistant defensive backs coach, secondary coach, and linebackers coach -- before replacing Johnson after his death in 2009.

Johnson, who was 68 when he lost a battle with cancer, was a little bit of a contradiction. When you saw his out-of-the-box schemes, it was easy to assume he had the personality of a mad scientist. You could picture him in a laboratory, hair all askew, with a crazy look in his eyes as he designed the antidotes to foil the Dallas Cowboys, New York Giants, Washington Redskins, and all of the other teams on the Eagles' schedule.

Yet nothing could have been further from the truth.

Johnson was a mostly unassuming, no-nonsense kind of guy. His tall, lanky frame made him an imposing presence, his deep voice commanding your attention and his tremendous insights into all aspects of football requiring that it be undivided. McDermott doesn't have Johnson's height or deep voice, but has benefitted greatly from a close-up view of the qualities that placed his mentor among the game's all-time great defensive coaches.

One of the biggest lessons McDermott learned is that the role of leading a defense, or a team, isn't about him. It was simply about working, with a great deal of dignity and class, to build a dominant scheme.

Not surprisingly, the signature of McDermott's scheme is similar to that of Johnson's. It features a 4-3 base and is known for being extremely aggressive. Opposing quarterbacks not only can expect to be blitzed, they can usually count on not knowing who is blitzing and the direction from which the blitzer is coming.

McDermott figures to get more production from his big men inside, Marcell Dareus and Kyle Williams, because they will have greater freedom to attack upfield and make plays than they did the past two years in Rex Ryan's linebacker-oriented 3-4 approach.

Jerry Hughes, who thrived in the 4-3 under Jim Schwartz in 2014, and Shaq Lawson are going to like their ability to consistently come flying off of the edges. And linebackers Preston Brown, Reggie Ragland, and (if he's re-signed) Lorenzo Alexander will relish the idea of being asked to blitz through various gaps without the burden of having to download an abundance of complex information on each play.

Calls and adjustments should be far more straightforward than they were under Ryan, thus minimizing the chances for having too few or too many men on the field during frequent personnel substitutions.

Like Johnson, McDermott coaches without fear. Like Johnson, he believes in his strategy and ability to get his players to execute it well.

That was a tremendous asset during his time as a defensive coordinator and should be every bit as helpful now that he's in charge of an entire team.

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