The team's ninth straight loss at Lincoln Financial Field dropped the Eagles to 3-4. Their three points were the lowest total for any Eagles team at home since Dec. 5, 2005.
The worst performance of Foles' career concluded after three quarters because of a head injury. The debut of rookie Matt Barkley will be remembered because he threw three interceptions in nine minutes.
Kelly's vaunted offense was listless throughout the afternoon, totaling a season-low 278 yards and spoiling a strong outing from the previously inconsistent defense.
"Everybody that coaches on the offensive side of the ball and everybody that played, we didn't play well enough today," Kelly said. "Obviously, scoring three points in this football game is not going to get it done."
It is unknown who will quarterback the Eagles next week against the New York Giants. Michael Vick missed his second consecutive game with a pulled left hamstring. Foles met with an independent neurologist, and Kelly did not know his status. Barkley looked like a fourth-round pick who was not ready to run an NFL offense, but he will start if both Vick and Foles remain ailing.
"I'm hoping we get them all back on Tuesday," Kelly said. "But I won't know until they get into the training room tomorrow."
If Foles had played well on Sunday, he might have made Kelly's decision about the starting quarterback job a challenge. But Foles finished 11 of 29 for 80 yards in three quarters. He also rushed for 25 yards. The decision-making and accuracy that were so impressive in last week's start were nowhere to be found.
Foles was unavailable to comment after the game. Kelly said his confidence in the second-year quarterback had not changed based on the performance.
"I think you have to look . . . through the whole body of work in terms of what he can do and can't do," Kelly said. "You hopefully like to chalk it up as just a bad day."
An ineffective running game did not help. LeSean McCoy totaled just 55 yards on 18 carries. Kelly said the blame could be spread around to "everybody on the offensive side of the ball," including himself for his play-calling.
After a first half that was an insult to offensive football - there were 13 punts before halftime - the Cowboys built a 10-0 lead on Phillip Tanner's 1-yard touchdown run early in the third quarter.
The Eagles shifted the momentum when DeMeco Ryans intercepted Tony Romo at the Eagles' 34-yard line and returned it 36 yards to the Cowboys 30.
They could have capitalized two plays later when Foles had Jason Avant wide open in the end zone, but Foles underthrew the receiver. The ball bounced off Avant's hands and was intercepted, although the call was overturned after officials concluded that it had hit the ground. But Avant was open enough that a good throw would have resulted in a touchdown.
"I saw the ball was thrown low, so I did my best to run to it and get to it," Avant said. "I got my back hand under it, but the nose hit the ground. Maybe if it had gotten the front of the ball, I could have scooped it up."
The Eagles then ran the ball for four straight plays before Foles threw an incompletion, setting up a third and 9 from the 9-yard line. Unable to quickly throw the ball, Foles tried buying time but was sacked along the sideline. The back of his head hit the turf, and he was later taken to the locker room for evaluation and ruled out for the game.
The Eagles wound up settling for a 31-yard Alex Henery field goal.
After receiver Terrance Williams caught a 9-yard touchdown pass to give Dallas a 17-3 lead, Barkley entered the game. Kelly admitted it was a "tough situation" for the rookie. Barkley proceeded to throw three interceptions and finished 11 of 20 for 129 yards.
"I think your mind-set has to be different when you come like that in the fourth quarter when your team's down, as opposed to when you're starting a game and it's 0-0 and you get in a rhythm," Barkley said. "I maybe was too aggressive on some of those throws trying to advance the ball downfield to help the team win. But I learned a lot from today."
The offense's issues overshadowed the defense's finest performance this season. The Eagles kept the Cowboys to 17 points on 368 yards, recorded two turnovers, and limited the Cowboys to 5 of 16 on third downs.
Kelly's offense was supposed to be a constant this season, but it lacked any firepower against the Cowboys. The quarterback situation went from a potential luxury to a potential catastrophe. First place will be harder to obtain, and an Eagles outlook that appeared promising at kickoff was gloomy by the final whistle.
"There was so much to gain from this game," McCoy said. "We just didn't get it done."
Languishing at the Linc
The Eagles lost their ninth straight game at Lincoln Financial Field on Sunday. Their last home victory was against the Giants, 19-14, on Sept. 30 of last year. The Eagles host the Giants on Sunday. Here is a look at their nine straight losses:
Cowboys 17, Eagles 3
Chiefs 26, Eagles 16
Chargers 33, Eagles 30
Redskins 27, Eagles 20
Bengals 34, Eagles 13
Panthers 30, Eagles 22
Cowboys 38, Eagles 23
Falcons 30, Eagles 17
Lions 26, Eagles 23, OT