When the Eagles held the Bills, Bears, Patriots and Seahawks to a combined 61 points over a four-game stretch, there was definitely reason for optimism regarding the Eagles’ defense.



Sure looked like they had figured a few things out.



They were up to 12th in the league in yards allowed and 15th in points allowed. Not great but considering everything? Not bad.



Since then?



The Eagles have allowed 81 points to three teams that are a combined 9-33.



The Eagles managed to win two of those three games because Carson Wentz engineered two late comebacks, but the defense will need to be significantly better Sunday than it has been to slow down a Cowboys offense that’s No. 1 in the NFL in yards per game, passing, yards per play, third down and sacks allowed.



A win over the Cowboys Sunday means the Eagles will win the NFC East just by beating the Giants on the last day of the season.



But can they pull it off with this defense?



Here’s a look at 10 issues facing the Eagles’ defense with the Cowboys heading to the Linc in three days.



RUN DEFENSE: A month and a half into season, this was one of the top run defenses in the league. Through six games, the Eagles were No. 2 against the run, allowing 3.3 yards per carry. In the last eight games they’re 22nd at 4.5 yards per carry. With one of the NFL’s best running teams coming to town Sunday. Definitely trending in the wrong direction.



INTERCEPTIONS: They’ve disappeared. The first seven games of the season, the Eagles had eight INTs — 5th-most in the NFL. They have just two the last seven games. Only the 49ers have fewer.



BIG PLAYS: The Eagles have allowed six TD passes of 50 yards or more, TWICE AS MANY AS ANY OTHER TEAM. Julio Jones, Terry McLaurin and Darius Slayton have all had their longest catch of the year against the Eagles. Case Keenum and Dwayne Haskins have both had their longest career TD pass against the Eagles. In all, the Eagles have allowed an NFL-high eight pass plays of at least 50 yards and an NFL-high nine scrimmage plays of 50 yards.



MALCOLM AND FLETCHER: Malcolm Jenkins and Fletcher Cox are the only truly elite defensive players the Eagles have. They're the only defensive players to make a Pro Bowl under the current coaching staff. Both have played OK this year but neither has been up to his usual standard. When you only have two elite players and neither has an elite year, that's a problem.



TORCHED BY BAD QBs: Over the last three weeks, the Eagles have faced a 37-year-old with his eighth team and a career record 30 games under .500, a hapless 38-year-old washed-up veteran who was benched two games into the season and a struggling 22-year-old rookie with three career TD passes. Those three — Ryan Fitzpatrick, Eli Manning and Dwayne Haskins — combined to torch the Eagles, completing 63 percent of their passes for 829 yards with 8 TDs, 1 INT and a 113.3 passer rating. How are you going to beat good QBs when you play like this against bad ones?



SACKS: The Eagles are 12th in the NFL in sacks, which is pretty good. But when you consider that 10 of them were against the Jets and they have 27 in their 13 other games, you get a more realistic picture of their inconsistent pass pressure. On Sunday in Washington, they faced a QB who had been sacked once every seven times he dropped back in his career. They didn’t sack him.



FIRST HALF: Jim Schwartz is one of the better defensive coaches when it comes to adjustments. The Eagles are 9th in the NFL in second-half defense, which is pretty good. But they’re 26th in first-half points allowed, and that’s routinely put the Eagles in early holes.



POINTS AFTER OFFENSE SCORES: I finally took the time to look this up, and as expected, the defense gives up way too many points after the offense scores. The offense has scored 61 times this year — 40 touchdowns and 21 field goals. Taking out nine instances when they scored in the final two minutes of a half, that’s 52 times that they’ve scored and then the defense has taken the field with a significant amount of time left in the half or game. Of those 52 times, they’ve allowed points 26 times. That's 20 TDs and 6 field goals on drives immediately following Eagles scores. On 99 drives that didn’t follow an offensive score, the defense has allowed points 32 times — 19 TDs and 13 field goals. So they're allowing points 50 percent of the time after the offense scores, 32 percent after the offense hasn't score. Following an offensive score, the defense is allowing 3.0 points per drive. Following non-scoring drives that figure drops to 1.7 points. Those are just momentum killers.



TRICK PLAYS: Whether it’s the Lions getting 44 yards from a receiver on an end-around to set up a field goal, the Patriots scoring a touchdown on a halfback option, the Seahawks scoring on a flea flicker or the Dolphins on a TD pass to their kicker, teams have had tremendous success using trick plays against the Eagles. They just seem to always fall for them.



PERSONNEL: It all comes down to this. Let’s be honest. A big part of the Eagles’ defensive struggles are simply due to them not having good enough players. They’ve found one Pro Bowl defensive player in their last 14 drafts, and that's Cox. How many other defensive players do they have who are among even the 10 best at their position? Malcolm Jenkins, maybe Brandon Graham? It's impossible to be a great defense without great players.

More on the Eagles