A defensive coordinator is typically a coach on a gridiron football team who is in charge of the defense. Generally, along with his offensive counterpart, he represents the second level of command structure after the head coach. The defensive coordinator is generally in charge of managing all defensive players and assistant coaches, of developing a general defensive game plan, and of calling the plays for the defense during the game. At higher levels of football (college and professional), the defensive coordinator typically has a number of assistant coaches working under him; usually coaches primarily responsible for the various defensive positions on the team (such defensive line, linebackers, or defensive backs).
James David "Buddy" Ryan is regarded as one of the most notable defensive coordinators in NFL history for implementing and perfecting the 46 defense. As the defensive coordinator for the Chicago Bears from 1978-1985, Ryan's 46 defense was a revolutionary scheme that helped the Bears win the 1985 Super Bowl XX. That 1985 Chicago Bears team is still considered one of the greatest teams in NFL history. Lead by their linebacking corps of Wilber Marshall, Otis Wilson and Hall of Famer Mike Singletary, the 1985 defense was first in scoring defense, only allowing 198 points in the regular season with an average of allowing only 12.4 points/game.
Monte Kiffin is an American defensive coordinator who has found success in both college and the NFL. He is widely regarded as the father of the Tampa 2 defense, a defensive scheme that he made famous during the late 1990's and early 2000's as the defensive coordinator for the Tampa Bay Buccaneers. Kiffin's defenses were notable for having extremely fast defensive backs that attacked the ball constantly. Relaying on a "bend-but-don't-break" mentality, his defenses cared more about limiting points than overall yards. As the Buccaneers defensive coordinator from 1996-2008, Kiffin, along with linebackers coach Lovie Smith, developed a feared defense that was the league's best in 2002. Led by Hall of Fame defensive tackle Warren Sapp, the 2002 defense was the first team in NFL history to lead the league in total defense, points allowed, and interceptions since the 1985 Chicago Bears. While the offense gradually improved, it was the defense that lead the Buccaneers to Super Bowl XXXVII against the Oakland Raiders where Tampa Bay won 48-21.