PITTSBURGH -- It looks like a coach Ken Whisenhunt worked with in Pittsburgh will be joining his staff in Tennessee.

And it won’t be Steelers linebackers coach Keith Butler.

Per ESPN NFL Insider Chris Mortensen, Ray Horton is the leading candidate to become the Titans’ new defensive coordinator, a position he held for two seasons in Arizona while Whisenhunt was the head coach.

Horton currently holds the same position with the Browns and is still under contract in Cleveland. But the former Steelers defensive backs coach has been given permission to pursue other opportunities, according to ESPN NFL Insider Adam Schefter, even though the Browns could block him from taking another job other than head coach.

There had been speculation that Whisenhunt would target Butler -- the two worked together on Bill Cowher’s staff in Pittsburgh -- after landing a second-head coaching job. But Butler, who turned down a chance to become the Dolphins’ defensive coordinator in 2010, still has a year left on his contract.

The Steelers can block a move by any of their assistant coaches under contact unless it is for a head-coaching job. Butler has long been seen as the heir apparent to Dick LeBeau as the Steelers’ defensive coordinator.

But with all signs pointing to the 76-year-old LeBeau returning in 2014, Butler will probably have to wait at least another year before becoming a defensive coordinator.