It was difficult to ascertain what exactly was going through DeMarco Murray's head as he watched the Eagles from the sideline in the fourth quarter.

The Cardinals had taken a 17-10 halftime lead and expanded it to a 27-point margin all in the matter of a quarter. Murray had little to do with the Eagles' success or failure to that point. He had just two third-quarter carries for 3 yards. And Ryan Mathews, who started ahead of him for the second straight week, had a costly fumble in that span.

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But what could clearly be seen on Murray's head was a ski cap as the Eagles offense took possession early in the fourth. His helmet wasn't anywhere within sight. Darren Sproles was on the field, and Mathews stood next to Murray, ready in case he was called by running backs coach Duce Staley.

"It was a little chilly out," Murray said, explaining the hat.

The DeMarco Demotion was in its third week, and the Eagles' prized free-agent running back has become even more of an afterthought for Chip Kelly and Staley. If there was any doubt before, there should be no longer: Murray is third on the depth chart.

"You've got to control what you can control and just keep grinding and fighting," Murray said. "It's out of my control."

The only numbers that matter: Cardinals 40, Eagles 17. But take a look at the running back distribution and that says it all about Murray's current place in the lineup. Mathews rushed 11 times for 58 yards. Sproles had six carries for 9 yards.

And Murray? He touched the ball only twice the entire game. Two carries for 3 yards. Last week against the Bills, Murray had 11 carries for 34 yards. The week before at New England, he logged eight rushes for 24 yards. But only two of 19 running back tries this week.

"The plan was we were going to rotate the running backs," Kelly said. "We didn't run the ball as much as we wanted to."

Murray said that he didn't know what his role would be before the game.

There has been the argument that Kelly hasn't adapted his offense to Murray's skill set. And maybe there's something to that. But he looks like a shot, 28-year-old running back. The Eagles owe Murray $8 million next season. Kelly is starting to make it conceivable that he'll simply cut his losses in the offseason.

It might be the correct move. Murray would surely welcome it. It appears that Kelly has lost the running back.

"Whoever is willing to have me," Murray said. "This is what I signed up for. So I'll be here."

It's a shame it took Kelly until the Patriots game to finally limit Murray's playing time. But it's not as if the Eagles' running game has been explosive since. Mathews hasn't looked the same since returning from a concussion last week. Sproles has been just mediocre.

Overall, the Eagles gained just 74 yards on 20 rushes. Kelly was forced to lean on Sam Bradford and the passing game once the Cardinals drifted away with the lead. But the Eagles didn't get enough going on the ground when it mattered in the first half - aside from Mathews' 20-yard bolt - and in particular on a crucial fourth down.

Kelly gambled late in the first half. The Eagles trailed by seven, and he must have figured he couldn't pass on a chance to net more than three points against one of the most explosive offenses in the NFL.

The Eagles had 1 yard to get. Mathews was the lone back. Bradford was under center. Riley Cooper motioned in to block. Mathews ran behind Cooper and to the right and was met almost immediately in the backfield. He gained no yards. The Eagles scored no points.

"We had Ryan in there. He's a 230-pound running back. I thought we were going to get it on fourth and 1," Kelly said.

If Murray has been efficient at anything this season, it's been on third down. He had been successful on 12 of 12 third downs of less than 4 yards this season. It's also fair to question whether Kelly should have had Bradford keep the ball and go for the first down.

But the Eagles offensive line has been inconsistent all season. Was there any reason to believe it could be dependable in that spot?

The Eagles' running-game woes have been a season-long problem, though. There were a few anomalous games, but Kelly's offseason decisions at running back and on the offensive line have continued to haunt him.

He invested poorly with Murray. But a more pertinent question may be how he would spend that much at a position in which backups routinely replace injured starters without the running game missing a beat. Look no further than the Cardinals for proof.

David Johnson has taken over for Chris Johnson and was solid in his first two starts. But he terrorized the Eagles defense on Sunday night, rushing for 187 yards on 29 carries. He scored three touchdowns on the ground.

Murray, meanwhile, seemed resigned to the fact that he wouldn't play again in the fourth. A series after Jordan Matthews caught a 78-yard touchdown pass, Murray wandered to the bench, took his ski cap off and grabbed his helmet. But as the drive continued and Sproles stayed on the field, Murray drifted farther from Kelly and Staley.

On the Eagles' next possession Murray's hat returned. What is going on underneath?

Murray felt the need to discuss his diminished role with Eagles owner Jeffrey Lurie last week. Does he want to be back next season even if he's being used as little as he is now?

He said he does. His sideline body language suggested otherwise.