Dallas Cowboys are on unfamiliar turf with committee of running backs

Reporting from OXNARD —  There’s a common thread that runs through most winning Dallas Cowboys teams, a hallmark of all that success.

A lone star in the offensive backfield.

Whether it was Tony Dorsett, Herschel Walker, Emmitt Smith, or most recently DeMarco Murray, the franchise typically has been at its best when it can put the ball in the hands of a superior back and watch him roll up yards.

Now, with Murray in Philadelphia after the Cowboys opted not to back up the Brinks truck for him, Dallas is in the somewhat unfamiliar position of leaning on a committee of running backs.

As training camp opens in Oxnard, the club is leaning mostly on third-year back Joseph Randle, but also fourth-year veteran Lance Dunbar and the oft-injured Darren McFadden to pick up the considerable slack minus Murray, who won the NFL’s rushing title last season with a Cowboys-record 1,845 yards.

“Most teams use a couple of different backs who contribute for them on first and second down, maybe they have a role guy who comes in on third down on passing situations,” Cowboys Coach Jason Garrett said. “So that’s been the trend in the league. Maybe because it’s such a demanding position physically, those guys get beaten up a lot. It’s a rare guy who can withstand that punishment with all those carries week in and week out.”

And that punishment comes at a cost. Murray, who signed a $42-million contract with the Eagles, had 392 carries in the 2014 regular season, the ninth-most in league history. The eight players ahead of him on that list encountered a dramatic statistical dropoff after workhorse seasons, averaging 831 yards fewer in the season that followed.

The Cowboys know this, of course, so it wasn’t just that Murray was too expensive for them — particularly with star quarterback Tony Romo and receiver Dez Bryant on the roster — but also because history indicates Murray is in line for a big step backward.

What’s more, there’s the notion that even a second-tier back could gain big yards behind that offensive line, the best in football, which includes three Pro Bowl players and two All-Pros.

The Cowboys have high hopes for Randle, who thrived in Murray’s shadow last season, averaging a staggering 6.7 yards on 51 carries. Off the field, the former Oklahoma State standout had significant issues lately, with a shoplifting arrest and a drug charge that was later dropped.

“When we did our homework on Joe, a lot of people thought Joe was one of the better backs they’d seen in a while in the Big 12,” said Stephen Jones, Cowboys director of player personnel and son of team owner Jerry Jones. “He’s had some things that obviously surfaced at times here, off the field he’s got to mature. He’s learned a lot this off-season, and according to the coaches they see a change. But he’s capable.”

Jerry Jones echoed that, saying Randle “has the potential to be the kind of back that would step in there and be your No. 1 back. If he were not here, then I wouldn’t feel as good as we go into the season and what might happen.”

Randle isn’t taking any risks by making bold promises. He was pleasant, but flat and dry as the Texas panhandle in his responses to reporters after practice this week.

“I’m going to approach every day and work as hard as I can,” he said. “I can’t worry about the outcome. Just going to focus on the day-to-day grind.”

McFadden, the former Oakland Raiders back, is with an unfamiliar team but in a familiar predicament — banged up. He’s nursing a bum hamstring and is on the Physically Unable to Perform list.

“He tweaked his hamstring maybe a couple of weeks ago and we don’t think it’s a serious thing,” Garrett said. “He’s working hard on his rehab and we just want to start with him being on PUP. We anticipate him being back sometime here in the next week or so.”

McFadden said he suffered the injury while running pass routes. He is coming off his first NFL season in which he appeared in all 16 games. In his previous six seasons, all with Oakland, he appeared in an average of 11 games per year.

“For me, it’s one of those things; I hate it happening right now,” he said of his latest injury. “But if I’m out there grinding, going 110% and trying to get better, it’s something that happened and I’m going to deal with it right now and just be ready to get back on the field when it’s time.”

Mostly, the Cowboys’ tailback situation is a fluid one, with no runaway favorite to shoulder the bulk of the load. In fact, late this week, three-time Pro Bowl back Steven Jackson, now a free agent, tweeted a picture of AT&T Stadium with a spotlight shining 39, his number, into the sky. It was meant to look like the beacon that summons Batman.

Jackson’s caption was simple, reading, “Attn: @Dallas Cowboys.”

At this point, though, these Cowboys aren’t ready to reach for the sky.

sam.farmer@latimes.com

Twitter: @LATimesfarmer