Adding to their injury woes, Dallas Cowboys running back Felix Jones sat out of practice Wednesday with a bruised left knee, leaving Dallas with fewer options in its backfield.

As they approach their NFC East showdown against the first place New York Giants on Sunday, Dallas may have to turn to rather inexperienced running backs: Phillip Tanner and Lance Dunbar.

Jones has done a serviceable job filling in over the last six quarters for starter DeMarco Murray, who suffered ligament damage in his left foot in Dallas’s loss to the Baltimore Ravens in Week Six.

Jones played the second half against Baltimore and rushed for 92 yards and a touchdown on 18 carries. In five games this season, he has 36 carries for 149 yards and one touchdown.

Murray was expected to miss only one game but was seen on crutches during practice Wednesday.

Tanner practiced with the first-team offense Wednesday and is the probable starter if Jones is sidelined. Tanner made the Cowboys roster as an undrafted free agent in 2011, and played in nine games as a rookie but injured his hamstring against Arizona in December and ended up on the injured reserve list.

Tanner’s experience is still rather limited despite two NFL seasons. He had 22 carries in 2011, and has 22 in 2012, for a career total of 137 yards on 44 carries.

Right behind Tanner is Dunbar, an undrafted rookie from North Texas University, who was signed to the practice squad after training camp, and called up on Oct. 8. During the preseason, Dunbar was second on the team in rushing with 106 yards and one touchdown on 18 carries.

Standing at 5-foot-8 and 191-pounds, Dunbar set a North Texas school record his senior year with 313 yards in a single game, and gained 1,115 yards and 10 touchdowns for the year. 

In his junior year, Dunbar also set the school record for most all-purpose yards in a season with 1,885 yards, and was eighth in the NCAA with 1,553 rushing yards.