Duce Staley is leaving the Eagles to become assistant head coach and running backs coach in Detroit, a source with knowledge of the situation said Monday. The title is the same one Staley held with the Eagles under former coach Doug Pederson.

Staley, who will turn 46 next month, wanted to move on after being bypassed for the head-coaching job in favor of Indianapolis offensive coordinator Nick Sirianni, a source said. Staley was the team’s longest-tenured assistant, having been hired by Andy Reid in 2011. He served under Reid, Chip Kelly, and Pederson.

Players appreciated Staley’s fiery, animated leadership. The Lions just hired a head coach, Dan Campbell, whose introductory news conference opened with a stirring call to arms right out of Braveheart, so they would seem to be well-matched.

“It [stinks],” Eagles defensive end Brandon Graham said Sunday when asked about Staley’s impending departure. “But I understand it. New coach, new people. Duce will be a good asset to a staff, wherever he goes.”

Running back Boston Scott spoke Sunday of how “very detail-oriented” Staley was in preparing his backs. “Selfishly, I would love for him to stay here and be with us,” Scott said, “but I would hope he does get an opportunity to have an increased role in a coaching staff, and stuff like that, because I really think his work is there. I just really hope he gets that shot.”

Staley was a third-round Eagles draft pick in 1997 and is the franchise’s fifth-leading rusher, with 1,200 carries for 4,807 yards in 98 Eagles games. He also caught 275 passes for 2,498 yards in those seven seasons.

In Detroit, he will be reunited with Hank Fraley, the Eagles’ center in Staley’s final three seasons with the team. Fraley is being retained as the Lions’ offensive line coach. Former Chargers head coach Anthony Lynn will be the offensive coordinator.