A year ago, the Eagles allowed only 68 points in the fourth quarter of games. Only the New York Giants forfeited as few in the NFL. Through four games this season, the Eagles have allowed 52 points in the last stanza. Only the Titans (56) have surrendered more.

"We were in the exact opposite position last year," Eagles defensive coordinator Jim Schwartz said on Tuesday. "Last year, we were struggling a little bit in the first half and in the second half we were pitching a shutout. There's a lot of layers to everything that goes on the football field. Fifty-two points in any quarter is too many."

As Schwartz noted, there have been many reasons why his defense hasn't been as stout in the fourth quarter. His unit allowed two touchdowns against the Chiefs and Giants only after the offense turned the ball over in Eagles territory. Each turnover came after three strong quarters of defense, and each set off a tidal wave of offense from each opponent.

But there was no such error from the offense this past week. Chargers quarterback Philip Rivers and company had the ball on two possessions – the first started in the third – and both resulted in long, touchdown-scoring drives in the fourth.

If it weren't for a 6-minute, 44 second drive that iced the game and kept the Chargers from getting the ball again, who knows if the 3-1 Eagles would have left Southern California with a 26-24 win.

But survive they did, even if a rash of injuries seemingly caught up on Schwartz's group.

"We've had our share of injury particularly in the back end," Eagles coach Doug Pederson said Monday. "And again, not to use that as an excuse, but young players are playing, and things are going to happen a little bit faster for them. It's something we've just got to continue to evaluate."

At cornerback, the Eagles have been without Ronald Darby since the opener and his initial replacement Jaylen Watkins since the second game. And at safety, they lost Rodney McLeod for a game and a half and his initial replacement Corey Graham for the last two games.

Rasul Douglas stepped in for Darby and Watkins and acquitted himself against the Chiefs and Giants, but the rookie struggled at the Chargers. Graham and Chris Maragos hung tough in place of McLeod, but each had breakdowns. And even though McLeod returned, he had inconsistencies – injury related or not – on Sunday.

But the absence of Fletcher Cox may be the No. 1 reason why the defense has regressed, and not just in the fourth quarter. Since the defensive tackle suffered a calf injury late in the second quarter of the Giants game, the Eagles have allowed 48 points over six-plus quarters and 7.5 yards per play.

In the just-under ten prior quarters, they allowed 37 points and 5.9 yards per play.

"I'm glad that didn't happen before he signed his contract because he probably would have asked for more," Schwartz said of Cox, who signed a six-year, $102.6 million deal in 2016. "That's a very frivolous way of saying we miss him and we need to do a better job of playing as a unit when guys like that are not in there."

Beau Allen (two tackles for loss, a sack, and quarterback hit) held his own starting against the Chargers. But Cox's presence alone forces offensive lines to pay more attention to the interior, which in turn gives the ends more one-on-one opportunities.

Chris Long is the only edge rusher to record a sack over the last two games and it came on the Chargers' opening drive. Rivers increasingly had time in the pocket as the game progressed, but conditioning would seem an unlikely excuse with the Eagles winning time of possession nearly 2 to 1.

"I certainly wouldn't place it on any kind of fatigue," Schwartz said.

The defensive coordinator mentioned penalties. The Eagles have been flagged six times in the second half over the last two games vs. only twice in the first two. But big plays have hurt more than anything. The Eagles have allowed more plays over 40 yards (six) than any team in the league.

Three alone came against the Chargers.

"Each of them was a different breakdown," Schwartz said.

The first big play came in the second quarter when Tyrell Williams caught a 75-yard touchdown. Douglas had the Chargers receiver off the line and took outside leverage in a zone coverage. It was unclear if he was supposed to receive help as Williams ran toward midfield. McLeod was underneath. Cornerback Jalen Mills was on the other side of the field, but the ball was caught on his half.

"I've sort of taken the approach this year of just saying everyone is a defensive breakdown, whether it's a little better rush, whether it's a little better coverage, whether it's a little better call," Schwartz said when asked to explain the coverage. "Bottom line is we gave up a long touchdown pass."

Douglas was clearly responsible for Keenan Allen's 49-yard catch before the half, though.

"We need to play more consistently at the corner position," Schwartz said. "It's not just about a singular flash play. It's about consistency over the course of the game."

Austin Ekeler's 35-yard touchdown run in the fourth came when he cut back against a slanting Chargers O-line and ran in between linebackers Jordan Hicks and Mychal Kendricks. And Allen's 50-yard catch and run later in the fourth came when McLeod apparently vacated the middle.

Injuries may have played a role in the recent slide, but every defense has its obstacles. Even good ones have blips. Schwartz hopes the Eagles' late-game struggles are just that.