Last season, after two weeks of offensive struggles, Chip Kelly opened up his playbook, tinkered with his base running plays, and resurrected a moribund ground game against the St. Louis Rams and then, most impressively, the next week against the New York Giants.

There were a few dips in production the rest of the season, but the Eagles never hit a valley as low as they did when they traveled to the 49ers in Week 4 and rushed for only 22 yards on 12 carries. Kelly was able to identify tendencies based on pre-snap formations and adjusted accordingly.

Last Sunday's meeting with the Cowboys was supposed to be the rebound game after a subpar effort in Atlanta. The Eagles coach dressed up some of his base runs, used different personnel packages, had Sam Bradford under center rather than in the shotgun, and called plays that weren't employed the week before.

Nothing worked.

When Kelly said that poor execution was the primary reason Eagles running backs were held to minus-2 yards on 15 carries against Dallas, he was right. But the changes he implemented last week didn't make a difference, either.

When the Eagles hike up to North Jersey to face the New York Jets on Sunday, Kelly will come closer to knowing whether culture does indeed beat scheme, because right now his offensive scheme doesn't inspire much confidence.

Dallas deserves a large share of the credit, but Kelly couldn't hide some predictability and the increasing probability that his base plays aren't as effective without a "read" option - a quarterback who can run with the ball.

With the immobile and fragile Sam Bradford at quarterback, there is no reason for an unblocked defender to account for him as a runner.

"When you keep [the read], that's an extra option, but I think we still have that," Bradford said. "We just haven't showed it."

Nick Foles and Mark Sanchez would at least keep a defense honest with a rush or two per game. But with so many plays still run with the quarterback in the shotgun - the traditional pre-snap look for the zone-read - the running back's path has become easy to detect.

For instance, the Eagles had nine inside runs against the Falcons - zone or man-to-man blocked - with the same "11" personnel package (one back, one tight end, three receivers) and out of the same formation: two receivers were on one side, left or right; a tight end was on the opposite side of the line with a receiver flanked to his outside; and a running back was on the same side of the quarterback as the tight end.

And each time, the tailback's path was toward the opposite side of the tight end. The Eagles gained only 21 yards - one play was called back by a holding penalty - on those carries.

It is the Eagles' bread-and-butter run play - one they practice more than any other - and one that has typically been successful. But some teams have been able to shut it down.

The other inside run used in Atlanta had two subtle differences - one of the two receivers away from the tight end motioned inside to help block, and the running back, now on the opposite side of the quarterback, ran toward the tight end.

The Eagles gained 12 yards - one was called back by a holding penalty - on two carries against Atlanta. It was the first play Kelly called against the Cowboys, but DeMarco Murray gained only 1 yard, and it was never heard from again.

The sweep was the only other run play Kelly called against Atlanta, but there was some variety in the formation and direction. The first attempt had three receivers split to the left and Murray running behind two pulling linemen. Blocks were missed, and he lost 12 yards. Kelly ditched the play.

He had more success with his base sweep play. The personnel was the same as the base inside-zone play, but the running back was on the opposite shoulder of the quarterback and ran to the tight end's side. Kelly called three straight on one drive and gained 58 yards - but a 19-yard gain was brought back by a hold.

Kelly dipped deeper into his bag of plays against the Cowboys. After the failed first carry, he ran the base inside-zone play with Bradford under center. Murray took the same path and gained only 3 yards.

Kelly later tried something different with the sweep. He had "21" personnel (two RBs, one TE, two WRs) and motioned Darren Sproles into the backfield with Mathews just before the shotgun snap. There was an inside zone with three receivers split one way. There were back-to-back inside zones from under center in which the running backs ran to the tight end side. Kelly went back to the sweep that worked in Atlanta. He even tried a stretch - the Cowboys' base run play and one Murray gobbled up yards on last season. Nothing worked.

Confidence had to be an issue by that point, but maybe a lack of comfort in the new plays and formations was an issue, as well.

"We try not to run a lot of plays, we try to major in the ones that we do," center Jason Kelce said. "That's been our MO since we've been here, and it's been something we've done very effectively."

Tackle Lane Johnson said the Eagles plan to utilize more of their arsenal. The outside zone used to be a valued play in the toolbox. The counter, jet sweep, and other plays were regulars in Kelly's game plans at Oregon. He has used the pistol or had his tailbacks hop from one side of the quarterback to the other to hide the running path.

But Kelly insists the inadequacies of the run game right now aren't because of tendencies.

"I think there are certain things that everybody does that are predictable from a tendency standpoint," he said. "When you line up in 'this' formation, 75 percent of the time you do 'this,' 25 percent of the time you do 'this.' There's nothing I don't think anybody does, offensively or defensively, that's 100 percent of the time."

The Eagles offense, though, has lost some of its unpredictability because package plays, which involve run and pass options that are decided post-snap, have been limited because Bradford isn't a threat to run. And with Bradford unable to check out of plays based on a defensive look, the offense faces even more constraints.

"We don't do a lot of audibling," Bradford said. "We go fast in this offense. That's kind of our advantage."

Kelly will tinker with his offense again, but slowing it down likely isn't on the table.

jmclane@phillynews.com

@Jeff_McLane