PHILADELPHIA — Duce Staley lead the Eagles’ backfield in 1999 as Andy Reid’s bell-cow running back, getting the ball on 325 carries. Doug Pederson started nine games at quarterback that year.

The Eagles have had starting running backs ranging from LeSean McCoy, Brian Westbrook to Darren Sproles and Jay Ajayi, and none of them — including Staley — reached that 325-carry benchmark in the 20 years since then.

That won’t happen in 2019, either, and maybe not for a long time in Philadelphia.

Coincidentally, Staley is playing a major role in that.

The Eagles started using a running back-by-committee approach toward the latter stages of Staley’s career in Philadelphia when he began splitting snaps with Correll Buckhalter and Brian Westbrook.

He was hired as the Eagles’ running backs coach for Chip Kelly in 2013 and had LeSean McCoy for a couple of years. When ‘Shady’ left in after 2014, so did the Eagles’ proclivity for bell-cows. Now, Reid’s running back philosophy has carried over to Pederson and Staley, and it’s not going anywhere.

“It’s been like that for a while around here," Staley said on Monday, “and it will continue to be.”

It was effective in the Eagles’ 2017 Super Bowl run, not so much in 2018 with lesser players and now, in 2019, the Eagles might have their first legitimate two-headed monster in a long time, with rookie Miles Sanders and veteran Jordan Howard leading the fray.

Well, Staley views it as a three-headed monster, with 36-year-old Darren Sproles still in the mix.

In Week 4, the Eagles went on the road to Green Bay and ran it down the Packers’ throat with their thunder-lightning combination of Howard and Sanders. That duo powered a rushing attack that gained 176 yards on 33 carries, or a 5.3 yards per carry average, with two touchdowns.

It was the most yardage the Eagles’ rushing attack has had since a near-identical line against the Chicago Bears in November 2017: 33 carries, 176 yards, one touchdown.

After shying away from the run at times early this season — and a lot of last season — don’t be surprised if the Eagles’ offense looks more like this in the coming weeks.

“I believe,” Pederson said on Friday, “it’s a little bit of a recipe for our offense.”

There was some confusion in the first few weeks this season as to why Howard wasn’t a bigger part of the offense. He only played 17 snaps in Week 1 and 18 in Week 2 with 14 combined carries.

That jumped to 33 snaps in Week 4 with 15 carries. He finished with 87 yards and two rushing touchdowns, adding another score through the air.

So, what took so long?

To misquote the Joker in “The Dark Knight” — it simply wasn’t all a part of the plan.

“Jordan is a great player and Jordan understands our rotation here. Every back does. We have a three-headed monster,” Staley said. “Each and every week the game-plan itself changes. You saw from Washington (in Week 1) what we were doing from that game-plan and moving forward. You saw what we we did last week against Green Bay.

“Each and every week we’re going to change those guys, we’re going to rotate those guys and we’re going to try to get the best guy in for that play call.”

Through four weeks, Sanders has been the constant. Even after putting the ball on the ground twice in one drive — with one of those fumbles going to the other team — in Week 3, the coaching staff has remained steadfast in its belief and confidence in the Penn State rookie. He was the Eagles’ highest running back draft pick since McCoy.

With the trio of Howard-Sanders-Sproles, the Eagles have a trio of running backs with complimentary skillsets like they haven’t had since that 2017 season when Jay Ajayi, LeGarrette Blount and Corey Clement comprised their three-headed monster.

That season, from Week 11 through the Super Bowl (discounting a meaningless Week 17), Ajayi averaged 13.3 touches per game, Blount averaged 9.7 and Clement averaged 5.3.

Expect this group to be skewed a bit heavier toward Howard and Sanders, with Sproles occasionally mixing in. As for their skills: Sanders is the shifty back, Howard is the power back and Sproles is the change-of-pace pass catcher.

Through four games, Sanders is averaging 12.5 touches, Howard 11.5 and Sproles 4.3.

Don’t try to figure out how this group might look in the coming weeks, though, because, week-to-week .... well, you never know.

“It’s based on the week,” Staley said. “You never know, next week it may be a lot of Jordan, a lot of Miles, the week after that it may just be Jordan sprinkled in with Miles. But they both know, all of them know, that it’s a rotation that’s constantly going.”

When Howard only played 17 snaps in Week 1, it was his fewest since the first game of his career in 2016 with the Bears. There, Howard had at least 10 carries in 41 of 48 games.

He’s already had less than 10 twice in two games, and it could happen again.

Jordan, you’re not in Chicago anymore.

“Don’t get it twisted: They want the ball,” Staley said. I want them to want the ball so when they get out there, they give their best. They never know when they going back out there. You want guys like that. You want guys that are driven, you want guys that leave everything on the field for their team.

“But you also want guys to understand the situation.”

Zack Rosenblatt may be reached at zrosenblatt@njadvancemedia.com. Follow him on Twitter @ZackBlatt. Find NJ.com on Facebook.