During a heartbreaking loss to the Baltimore Ravens on Sunday, the Dallas Cowboys may have lost one of their biggest playmakers for an extended period of time.

DeMarco Murray left the Week 6 contest with a foot injury, registering just one carry in the second half. He dominated a usually stingy Ravens run defense in the first half, picking up 93 rushing yards on 14 carries.

ESPN Dallas reports that X-rays were negative, and Murray won’t miss the whole season because of the Lisfranc injury. Still, Dallas fears their starter suffered ligament damage in his foot, and he could be out for a while.

Murray’s rookie season was cut short by an injury. He fractured his ankle against the Giants, and was forced to watch the Cowboys miss the playoffs.

If Murray is unable to take the field for a few weeks, the Cowboys will need one of their reserves to step up in his absence. Tony Romo has struggled this year, throwing more interceptions than touchdowns. He’ll have a very tough time leading Dallas to the postseason with a subpar running game. The Cowboys currently sit by themselves in last place in the NFC East.

The most likely candidate to get the starting nod is Felix Jones. Jones has had success when sharing carries, but has had trouble when asked to be the No.1 rusher.

In relief of Murray, Jones had his best game of 2012. He picked up 92 yards on 18 carries, including one touchdown. Jones also caught a pass for 13 yards.

Jones isn’t a very big running back. Standing at just 5-foot-10, it’s hard for him to take a lot of punishment and be effective. He’s also had conditioning issues, and was forced to miss snaps in Baltimore because of cramps.

Because of his durability issues, Jones will need some assistance in Murray’s absence.

Phillip Tanner would probably get the call to be Jones’ immediate backup. He hadn’t run the ball once this season, before Sunday, but got the call nine times with Murray out.

It’s not known exactly how long Murray will be out, but the Cowboys are preparing for the worst. They play in one of the toughest divisions in the NFL, and will need someone to step up to have a shot at making the playoffs.

Murray won’t be easily replaced. He is considered to be one of the top running backs in the league, averaging 5.13 yards per carry for his career.

In Week 7, Dallas will visit Cam Newton and Carolina.