A number of reasons factored into Reid's decision, according to team sources. The coach had felt McDermott struggled with following in the footsteps of the esteemed Jim Johnson, who died in July 2009. McDermott's inexperience was also a factor.
Ultimately, it was the defense's poor showings against Minnesota, which cost the Eagles a bye, and in the playoff loss to Green Bay that did in McDermott.
While the firing did not become official until Saturday, the decision was made on Wednesday, with Reid informing him the next day, a league source said. The Eagles had hoped to buy the 36-year-old McDermott some extra time to look for another job.
On Monday, just a day after the Eagles' season ended with a 21-16 playoff loss to the Packers, McDermott still had a job. On that day Reid was asked directly if his defensive coordinator would be back.
"Yeah," he said.
Earlier, the head coach was asked to assess McDermott's season, in light of the fact that the defense had allowed a franchise-high 31 touchdown passes, and finished the regular season with the worst red-zone efficiency in the NFL since 1988.
"You're dealing with a guy that's a tremendous worker and is a very smart individual," Reid said then. "And so I look at it a little bit different than what you do in that I've seen him work with young guys, I've seen him work through injuries, I've seen him stay positive through those situations and still put us in a position to win football games."
Reid's vote of confidence, however, was no more than the coach trying to buy some time. He had yet to meet with McDermott and did not want to publicly fire his onetime assistant, team sources said.
But it's not as if Reid hasn't said one thing only to do another over the last year. Most of his reversals, though, have had to do with the quarterback position. This was one of his coordinators. Reid had not fired an offensive or defensive coordinator in his 12 seasons with the Eagles.
He did oust special-teams coordinator Ted Daisher last year so that he could hire Bobby April for that post.
A growing list of unemployed defensive coordinators also played into Reid's decision, team sources said. While the 60-year-old Jauron, who coached the Eagles' defensive backs this past season, is considered a leading contender for the opening, there are a number of other possible candidates.
Former Browns defensive coordinator Rob Ryan and ex-49ers head coach Mike Singletary are for hire.
Jauron is scheduled to interview with the Browns this week for their vacant defensive coordinator position. He previously worked under Cleveland president Mike Holmgren in Green Bay and had head coaching stints in Buffalo (2006-09) and Chicago (1999-2003). Reid hired Jauron last January to bring a veteran voice to the defense.
McDermott, meanwhile, joins the above unemployed. Hired by the Eagles originally as an intern, the La Salle High product worked his way up the coaching ladder under the tutelage of Johnson.
Four assistants under Johnson - John Harbaugh, Steve Spagnuolo, Leslie Frazier, and Ron Rivera - went on to become either coordinators or head coaches elsewhere. Frazier and Rivera were recently named head coaches in Minnesota and Carolina. So when Johnson's cancer was diagnosed in January 2009, McDermott was the natural successor for a head coach that likes to promote from within.
In July 2009, just days before Johnson died, McDermott was named his successor. He adopted his predecessor's aggressive, blitzing style, but his approach was different in many other ways. McDermott liked to tinker with his defense and substitute players in and out during a game.
A few defensive players privately complained about their roles in the young coordinator's scheme. McDermott, though, dealt with a number of significant injuries - six starters were lost at various points during this season - and a young cast of players.
But the defense got progressively worse as each of the last two seasons wore down. Against the Vikings, the unit struggled against third-string quarterback Joe Webb, who was making his first career start. In the season-ending loss to the Packers, running back James Starks, in just his fifth NFL game, gutted the Eagles for 123 rushing yards.
"Honestly, the last I heard he was coming back," Eagles defensive end Darryl Tapp said. "Yeah, I'm disappointed. You work with a guy all year long you get to like him. But this is the business we work in."
Contact staff writer Jeff McLane at 215-854-4745 or email@example.com. Follow him on Twitter at www.twitter.com/Jeff_McLane.