CHICAGO — The playoff performance of Philadelphia Eagles quarterback/folk hero/miracle worker Nick Foles has become almost mystical in nature, a phenomenon easier to marvel at than explain. He is a career backup who became a Super Bowl MVP, returned to holding clipboards and was again called in to save another season.

Foles’s logic-defying emergence has defined the Eagles’ postseason excellence for two seasons, most recently with his game-winning touchdown pass on a fourth-and-two play in the final minute of Sunday’s opening-round win over the Chicago Bears.

His story, though, should not be mistaken for the Eagles’ driving force. There is nothing magical about Fletcher Cox, Michael Bennett and the rest of the Eagles’ defensive front seven.

While Foles justifiably hogs headlines, the primary reason to take the Eagles’ Super Bowl defense seriously resides on the other side of the ball. The Eagles’ defense, stacked with stars and surging after a midseason, injury-riddled swoon, carries far less intrigue than Foles seizing fame as an understudy. But if the Eagles return to the Super Bowl, Philadelphia’s defense will deserve a fair share of the credit.

During last year’s Super Bowl run, the Eagles surrendered 10 points to the Falcons and seven to the Vikings. They yielded 33 in the Super Bowl to the Patriots, but the defense also sealed the victory when defensive end Brandon Graham strip-sacked Tom Brady. Sunday against the Bears, they limited Chicago to 15 points and forced a three-and-out that set up Foles’s game-winning drive. Foles has delivered magic, but Philadelphia’s defense has been an equal partner.

“I think what people misunderstand is, there’s always a chip on our shoulder,” Eagles safety Malcolm Jenkins said. “This is just one of many weeks people have doubted us that don’t pay attention to what we do defensively. They draw attention to all these other things, but we know how to compete. We really don’t care about that. We know who we are.”

Jenkins may have drawn inspiration from those who doubted, but as defensive end Chris Long said, “We’ve given them reason at some points.”

The Eagles suffered a wave of injuries to their defense, particularly in the secondary, where they lost their top three cornerbacks (Ronald Darby, Jalen Mills and Sidney Jones) and safety Rodney McLeod. As they filled in with rookie Avonte Maddox and former practice squad player Cre’Von LeBlanc at cornerback, and a carousel of reserves next to Jenkins at safety, the Eagles’ defense wilted, bottoming out with a 48-7 beating at the hands of the New Orleans Saints, their next playoff opponent.

“Some key spots have been down,” Long said. “People are always afraid to make an excuse, but we just won a playoff game. So it’s not an excuse. You look at the list of players we lost on the back end this year, it’s been tough. Those young guys came in and did a good job fighting, adapting. A lot of them are helping us win right now.”

The Eagles’ late-season defensive improvement does not owe to a return to health. While the return of defensive tackle Timmy Jernigan is significant, the Eagles will have pretty much the same personnel for this game against the Saints as the disastrous meeting in November. But the Eagles say they’re better now, because those players forced into action have grown.

“We say ‘next man up,’ ” Coach Doug Pederson said. “This year has been ‘next man, and maybe even the second man up.’ Right now, you’re seeing these guys playing more minutes and getting more comfortable with the scheme.”

Those cornerbacks could still be their downfall. Against the Bears, Mitchell Trubisky completed 18 of the 28 passes on which he targeted wide receivers for 248 yards, including five completions of at least 20 yards. On Chicago’s fourth-quarter, go-ahead touchdown drive, Maddox yielded consecutive gains of 34 and 22 yards, the latter a touchdown on which he also committed pass interference.

If Trubisky can capitalize on Philadelphia’s corners outdoors at Soldier Field, Drew Brees could vaporize them inside the Superdome. But Pederson insists the Eagles can handle the Saints now.

“I think you’ve got to look at where we’ve come from and what we’ve done,” Pederson said. “Just the way this team has come together at the end of the regular season. This team believes. This team believes in everything that we’re doing. And we’re different. It’s a different mind-set. It’s a different football team. We’re a different group than when we played New Orleans the first time.”

To beat the Saints, the Eagles will have to rely on their strength. Even when Carson Wentz is healthy, and even when Foles is dabbling in wizardry, the Eagles are built on their defensive line. Cox is the Eagles’ best player, perhaps the best defensive lineman this side of Aaron Donald. Bennett and Jernigan both excel at collapsing pockets and stuffing runs. Long is a key edge rusher, as is Graham.

And, if that fails, they can hope Foles conjures more fairy dust. In the nine games Foles has played either in the playoffs or facing playoff elimination (including his first stint with the team from 2012 to 2014), the Eagles are 8-1. In those games, he has completed 72 percent of his passes for 2,657 yards with 18 touchdown passes and six interceptions.

If Foles wins yet again, his march to another NFC championship game will be viewed as a fairy tale. Really, it is the deep roster around him making it possible, starting with a defense eager to prove itself again.

“Here’s where we can put our stamp on who we are,” Long said. “We’ve had some low points during the year, but I think we’ve got some guys back healthy, and we’ve done some things different.”

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