A source confirmed on Friday that Jets defensive coordinator Mike Pettine turned down a contract extension from the team months ago.

This is a sign that Pettine, who is in the final year of his deal, plans on departing the Jets after this season to get out of Rex Ryan’s shadow and improve his chances of becoming a head coach.

Pettine was a defensive line and linebackers coach in Baltimore, where Ryan was the defensive coordinator. When Ryan got the head coaching job with the Jets before the 2009 season, Pettine came with him to serve as the defensive coordinator.

Pettine’s potential departure adds another layer of uncertainty for a Jets team filled with question marks heading into the offseason.

Pettine’s unit helped push the Jets to back-to-back AFC Championship games in 2009 and 2010 when they finished first and third in total defense, respectively. In 2011, the Jets were fifth in the league and are eighth this season, even with top CB Darrelle Revis being sidelined since Week 3 with a torn ACL.