The Eagles could move into a tie for the NFL’s best record on Monday night, but that doesn’t mean everything has been going swimmingly in Philadelphia.

Back-to-back blowout losses have rocked the defending NFC champions, with the 49ers and Cowboys both cruising to wins over the Eagles and damaging the team’s status as NFC favorites. With San Francisco now favored to win the conference and in position to earn the No. 1 seed, changes have arrived for Nick Sirianni’s team.

As first reported by Fox Sports’ Jay Glazer on Sunday, the Eagles quietly made a major change to their defensive coaching staff leading up to Monday night’s game against the Seahawks.

Here’s what you need to know about who is leading the Eagles’ defense and why a change was made.

Who is the Eagles’ defensive coordinator?

Sean Desai remains the Eagles’ defensive coordinator, but his role has changed significantly. After reports from Glazer and other outlets, the Eagles confirmed that former Lions head coach Matt Patricia will serve as the team’s defensive play-caller starting in Week 15.

Desai, meanwhile, is moving up to the coaching booth while Patricia will be on the sidelines. While Patricia doesn’t have the title of defensive coordinator, he is the team’s de facto defensive coordinator.

Patricia, of course, is familiar with ambiguity surrounding his role. He was the Patriots’ offensive play-caller in 2022 but never held the title of offensive coordinator as Bill Belichick refused to go into detail about who would be calling the plays. Patricia didn’t find much success in the role, and he joined Sirianni’s staff as a senior defensive assistant in April.

Patricia served as the Patriots’ defensive coordinator from 2012-17, after six years as a defensive position coach on Belichick’s staff. New England won two Super Bowls with Patricia calling the defensive plays, though his defense famously struggled against Nick Foles and the Eagles in Super Bowl 52. Patricia became the Lions’ head coach the following day, though he lasted less than three years in Detroit.

Desai is in his second stint as an NFL defensive coordinator, as he led the Bears’ defense in 2021 before building his reputation as associate head coach with the Seahawks in 2022.

Here’s a closer look at why the Eagles made a switch despite their strong record.

Why Matt Patricia replaced Sean Desai as Eagles’ defensive play-caller

For most of the season, the Eagles coordinator that has received the brunt of criticism from fans was offensive play-caller Brian Johnson. While Johnson still might not have the offense running anything like it did last season — Philadelphia scored a combined 32 points in its last two games — it was the defense that became a trouble spot in recent weeks.

The Eagles surrendered 34 points and a whopping 505 yards in a loss to the Bills before getting torched by the 49ers to the tune of 42 points the following week. Those performances started to look more like a pattern than a fluke when the Cowboys put 24 points on the board in the first half alone against the Eagles in a Week 14 rout.

Philadelphia’s secondary was a strength for much of 2022, when Jonathan Gannon was the team’s defensive coordinator, but it’s the secondary that has taken a major step back in recent weeks. CB James Bradberry hasn’t been able to recapture the success he found in 2022, while Darius Slay has dealt with more inconsistency than he’s accustomed to.

The news came just a day after a report from The Athletic detailed how players were taking control of the scouting ahead of Monday’s matchup with the Seahawks. Safety Kevin Byard, acquired in October, asked Desai to let the secondary handle the matchup’s scouting report themselves.

While Byard deflected blame onto the players, telling The Athletic, “We all have our hands in the same pot” and emphasizing that coaches alone shouldn’t take responsibility for the defense’s struggles, Sirianni made a call sometime between the loss to the Cowboys and Sunday morning to make a more comprehensive change.