The Arizona Cardinals are expected to formally approach the Pittsburgh Steelers for permission to interview linebackers coach Keith Butler regarding their defensive coordinator vacancy, Jason La Canfora of the NFL Network reports.

La Canfora adds that the Steelers are not expected to block the move.

Pittsburgh's linebackers coach since 2003, Butler has been linked to the Cardinals ever since former Steelers assistant Ken Whisenhunt became their head coach in 2007.

During Super Bowl XLV's Media Day last Tuesday, Butler disclosed that there are no clauses in his contract that would make him the defensive coordinator-in-waiting in Pittsburgh.

Dick LeBeau, the Steelers' 73-year old defensive coordinator, has an expiring contract, but does not appear ready to hang up his whistle.