Doug Marrone was officially introduced as head coach of the Buffalo Bills today. Per multiple reports, he's already requested permission to interview a defensive coordinator candidate.

FootballScoop.com reports (later confirmed by ESPN's Rich Cimini) that the Bills have requested permission to interview New York Jets defensive coordinator Mike Pettine, whose contract is set to expire in short order.

Pettine, 46, has spent the past four seasons as the Jets' defensive coordinator, where he has worked under venerable defensive mind Rex Ryan. Prior to that, Pettine spent seven years as a defensive assistant with the Baltimore Ravens, working himself up from low man on the totem pole to the outside linebackers coach before he followed Ryan to New York. All told, Pettine has worked closely with Ryan all 11 seasons he's been at the NFL level.

Typically, NFL teams can block lateral moves - but because Pettine's contract is set to expire, making him a coaching free agent, that option is essentially off the table.

Ryan's defense - and by extension, Pettine's - is popularly known as an exotic and extremely aggressive attack that works out of a 3-4 base. This past season, however, the Jets committed to playing more four-man lines because of the rising popularity of the passing game and the spread offense, particularly in the AFC East. In four years on the job, the Jets have finished in the Top 8 defensively every season, including three Top 5 finishes a No. 1 overall finish in 2009.

Who Marrone brings in to call the shots defensively is of critical importance. Pettine might be the first name on the list.