The hiring of Monte Kiffin as the Dallas Cowboys defensive coordinator makes him tied as the second-oldest assistant coach in the NFL at 72
Kiffin turns 73 on February 29.
Kiffin is tied for the second oldest in the NFL with Philadelphia Eagles defensive line coach Tommy Brasher, who came out of retirement in the last few weeks of the 2012 season.
The oldest assistant coach in the NFL is Pittsburgh Steelers defensive coordinator Dick LeBeau, who is 75.
Incidentally, Eagles offensive line coach Howard Mudd is 70.
Brasher and Mudd could retire again, leaving LeBeau and Kiffin as the oldest assistants in the league.