Dallas Cowboys owner Jerry Jones and coach Jason Garrett have focused their search for a defensive coordinator on longtime NFL assistant Monte Kiffin, according to team and league sources.

Kiffin was at the Cowboys' Valley Ranch facility on Thursday and met with Jones and Garrett, according to sources.

It is unknown whether the 72-year-old Kiffin has been offered the job, but he has emerged as the leading candidate from a list that also includes Ray Horton, the former Cowboys player and current Cardinals defensive coordinator who has interviewed for several head coaching positions recently.

If Kiffin is hired, the Cowboys would be switching from a 3-4 defensive front to a 4-3, forcing pass-rusher DeMarcus Ware to play defensive end, with his hand on the ground for the first time in his career.

Kiffin resigned as defensive coordinator at USC, where his son, Lane, is the head coach, and expressed his desire to return to the NFL.