The backfield was always supposed to be a strength for the New Orleans Saints this season.

But how that played out through the first quarter of the season might come as a surprise.

Bottled up at times on the ground, the trio of Mark Ingram, C.J. Spiller and Khiry Robinson has been dangerous through the air, a development that could be key as the Saints (1-3) head into another must-win game on the road at noon Sunday against the reeling Philadelphia Eagles (1-3).

“I think the three-man punch that we have going with Mark, Khiry and now C.J. really gives us a lot of elements,” quarterback Drew Brees said. “We’ve got a lot of confidence in all of those guys doing a lot of different things.”

First and foremost, New Orleans needs to get its running game going. Philadelphia ranks 13th in the league against the run, allowing 97 yards per game and just 3.3 yards per carry.

New Orleans, on the other hand, has struggled, in large part because of an offensive line that has had trouble creating holes. Despite a 77-yard performance from Ingram last week in a win over the Dallas Cowboys, the Saints rank a paltry 28th in the NFL in rushing at 82.8 yards per game.

But even with the running game struggling, the Saints backs have found a way to make an impact.

Ingram, in particular, has been a revelation as a receiver out of the backfield. Until this season, Ingram had been an afterthought in the passing game.

His career high for receptions was a pedestrian 29, recorded last year after the Saints parted ways with Darren Sproles, now with the Eagles.

Ingram, whose father was an NFL receiver, always maintained he could do more in the passing game.

A quarter of the way into the season, Ingram is backing up that talk with plenty of action. Ingram leads all NFL running backs with 22 receptions, and his production in the passing game (203 yards) is almost identical to his production on the ground (204 yards).

Ingram ranks fifth among NFL running backs in total yardage through the first four games, trailing only Adrian Peterson, Matt Forte, Jamaal Charles and Devonta Freeman.

“To watch his development from when he first came in to now, obviously he carries the load for us in a lot of cases in the backfield,” Brees said. “Out of the backfield, I think he is a very good receiver. I think he is a very patient receiver. He has come a long way.”

Patience is an underrated virtue for a pass-catching running back, particularly in the screen game.

NFL defenders are accustomed to recognizing screens; the offensive line and the back’s movement often give away the play.

Ingram, though, has an innate understanding of how to set up a route and wait until the final moment to show what he intends to do.

“Even as a back coming out of the backfield, routes need to be set up,” Brees said. “There are times when you could be too quick getting into something. You have to allow things to unfold and allow things to express themselves a little bit, and then you’re able to get that matchup or that space that is going to allow you to get open.”

Spiller is a different type of weapon. After his injury-related absence from most of training camp — and perhaps a sense of the unknown — Spiller spent most of the season’s first quarter relatively silent, save for a brief glimpse of his open-field ability here and there.

Then, in one brilliant, game-winning play in overtime last Sunday against the Cowboys, Spiller’s potential impact came into focus.

Used heavily, Spiller could be every bit the weapon that Reggie Bush or Darren Sproles once was for the Saints offense. Spiller’s ability in the open field forces defenses to make a move; a safety or defensive back has to be brought close to the line to deal with him, opening possibilities for receivers downfield.

“I know he’s got that speed, and I think the challenge sometimes is how you handle someone like him when you’re into extended sets,” Payton said “The other night (against Dallas) was a man-to-man look with a linebacker moving out to cover him. So a lot depends on who else is on the field with him; I would say that’s critical.”

The New Orleans running backs could play a key role against a Philadelphia defense ill-equipped to cover Ingram or Spiller out of the backfield.

The Eagles’ top two linebackers — Kiko Alonso and Mychal Kendricks — will miss Sunday’s game because of injury. Without them, Philadelphia likely will have to get creative or risk getting carved up by underneath routes.

And if the Saints can finally get the running game going, their short, high-percentage passing game will be even more effective.