"I have had the opportunity to get to know Sean Payton and his staff a bit better recently and I am excited about joining the team," Ryan said in a statement provided by the Saints. "I'm ready to get to work on all facets of the game. This is a great opportunity and we're getting started right away."
When Payton took over as head coach in 2006, New Orleans had a 4-3 scheme overseen by Gary Gibbs, who was fired after the 2008 season. In 2009, Payton brought in Gregg Williams, whose hybrid scheme used a 4-3 base alignment but switched to a 3-4 in certain situations, usually on passing downs in order to help disguise which player might be blitzing.
Williams left after the 2011 season, and months later was suspended along with Payton, general manager Mickey Loomis and Saints assistant head coach Joe Vitt by NFL Commissioner Roger Goodell in connection with the league's bounty probe.
The NFL said Williams ran the bounty pool and gave him an indefinite suspension. He was reinstated this past week and hired as a top defensive coach by Tennessee.
Williams has long proclaimed himself a disciple of Buddy Ryan, who was the defensive coordinator of the Super Bowl champion Chicago Bears in 1985 and later served as head coach of the Philadelphia Eagles and Arizona Cardinals.
Williams often spoke of wanting his defenses to be "nasty" and used mottos like "defenses are respected when they're feared."
Now, a little more than a year after letting go of Williams, Payton has brought in the son of Williams' mentor.
Rob Ryan got his start in the NFL on his father's Arizona staff in 1994. He later spent three seasons as defensive coordinator at Oklahoma State before returning to the NFL with New England, under Bill Belichick, in 2000.