After losing just three games in 2017, the defending Super Bowl champion Philadelphia Eagles lost their fourth game of the 2018 season on Sunday, and now they've lost even more.

According to ESPN's Adam Schefter, the Eagles won't have starting defensive end Derek Barnett for the rest of the year, as the former first-round draft pick is set to undergo surgery for a season-ending shoulder injury.

Barnett had been listed on the team's injury report and missed a game with a shoulder ailment in recent weeks, but it now appears the pass rusher will be headed to Injured Reserve. Although his 17 tackles and 2.5 sacks through six games roughly put him on pace to just match his rookie numbers from a year ago, the ex-Tennessee standout had been among the Eagles' most consistent edge rushers this year. And while Philadelphia is probably best equipped to lose a starter at defensive end, where they also have Brandon Graham, Chris Long and a heating-up Michael Bennett, Barnett's loss is but one of countless big injury blows the Birds have sustained in 2018.

As PhillyVoice's Jimmy Kempski noted, the following Eagles were already on indefinite injury lists -- sidelined for most of, if not the entire, season -- before Barnett's reported surgery: Jay Ajayi, Mack Hollins, Mike Wallace, Richard Rodgers, Tim Jernigan, Chris Maragos and Rodney McLeod.

In Barnett's anticipated absence, Bennett figures to start opposite Graham, with Long and fourth-round rookie Josh Sweat coming off the bench.