Chip Kelly confirmed Wednesday that DeMarco Murray was frustrated with his playing time after the Patriots game. That raises the question: Is the running back also frustrated with the Eagles offense?

Kelly's scheme, after all, has played a significant role in Murray's decline after he led the NFL in rushing last season. There are, of course, many other reasons he is last in the league in yards per carry (3.5 average) among running backs with more than 125 rushes.

But the Eagles offense is vastly different from the Cowboys', and Kelly has tried only on occasion to incorporate some of the plays and techniques Murray was comfortable with in Dallas into his system.

Murray has been asked about his comfort in the Eagles offense almost from the moment he arrived. He has said little publicly to suggest that he doesn't think the scheme is suited to his skill set, but a source close to him said that Murray has struggled with receiving the majority of his handoffs from the shotgun as opposed to under center.

Kelly said he spoke to Murray about his role both before and after the Patriots game, in which he had fewer carries than Darren Sproles and Kenjon Barner. The tailback also spoke to Eagles owner Jeffrey Lurie on the flight home, but Kelly downplayed the conversation. It's unclear whether the machinations of the offense were also discussed.

Murray, for the second straight day, declined to answer questions. He typically talks on Thursdays. "Same routine," he said.

Kelly won't say Murray will return to being the primary ballcarrier, but it is unlikely he will bury him on the depth chart. While he clearly hasn't produced at the same level, Murray still can be effective and the Eagles need to get him going for the stretch run. He may be their best receiver out of the backfield.

And there is, of course, his contract. Murray has a $7 million salary next season, all of which is guaranteed, and the Eagles would take a $13 million salary cap hit if they were to simply release him. A trade of an aging running back at that number would be virtually impossible.

The other number that prevents him from having trade value, aside from his basic rushing statistics (163 carries for 569 yards and four touchdowns), is his DYAR (defense-adjusted yards above replacement) number from this year compared with last.

Football Outsiders calculates DYAR as "the value of the performance on plays where [the] running back carried the ball compared to the replacement level, adjusted for situation and opponent and then translated into yardage."

It's advanced statistics, but it's also a more accurate gauge. Murray's DYAR last season was 382; this year it's minus-10. While those may seem like arbitrary numbers, Murray was first among 43 running backs last year and he's 30th out of 39 this year.

LeSean McCoy, by comparison, is fourth this year and was 15th last year.

Kelly checked off injuries as one reason for Murray's struggles. He also mentioned dropped passes from receivers.

"I think everybody has contributed," Kelly said. "We're not exactly where we want to be offensively from any aspect."

But Sproles (3.8 rushing average), Barner (4.6), and especially Ryan Mathews (5.7) haven't performed as poorly. Sproles (86) and Mathews (62), despite getting 62 and 54 percent fewer carries, have higher DYARs than Murray.

Kelly said that each game had to be looked at individually, but after three-fourths of the season there is a large enough sample. Every running back has essentially played behind the same inconsistent offensive line and had to deal with the same inefficient passing offense.

According to Kelly, Murray's production on the ground last season - he rushed for 1,845 yards - was a byproduct of the Cowboys' overall offensive success.

"You've got a wide receiver outside that's going to get doubled on every play because he may be the best receiver in the game in Dez Bryant," Kelly said. "You've got a Hall of Fame tight end [Jason Witten]. It's a different dynamic in terms of how people defended Dallas [and] in terms of how people defend us."

But those aren't the only differences. The Cowboys ran 91 percent of their run plays from under center as opposed to the shotgun. The Eagles have run only 14 percent from under center.

"I know [Murray] had 42 carries from the gun for 206 yards [last season], so for a 4.8-yard average," said Kelly, who also pointed out that Murray played in a college system where shotgun handoffs were the norm.

But, as Kelly said, you can't compare the Cowboys offense - and certainly a college one - to that of the Eagles. And that may have been where Kelly went wrong in his evaluation of Murray this offseason. Murray actually has a better average from the shotgun (3.7) than he does from under center (2.6) this season, but the Eagles run so few plays from the latter that it's difficult to draw any conclusions.

They've hardly used the play-action pass when Sam Bradford or Mark Sanchez has been under center, so defenses have been able to play downhill when the Eagles have been in that formation. Sproles said having the quarterback under center allows the running back to start deeper and get more of a running start, and "if you have to cut back you can see [the hole] more."

The extra running room can be helpful for stretch and counter sweeps - plays the Cowboys often used with Murray. Kelly has done a little of those, but his offensive line is better equipped for zone-blocking.

"He knew coming in, just like we knew coming in, what we were going to do," Kelly said of Murray. "We never had any discussion that we were going to change our system, you know?"

Maybe they should have.