IRVING, Texas — The Dallas Cowboys received another blow to their offense when they discovered rookie running back Felix Jones will be out two to four weeks with a left hamstring injury.

Jones suffered the injury after a 14-yard run in the third quarter during the Cowboys' loss at Arizona.

Jones tried to stretch the hamstring on the sideline but didn't return.

Coach Wade Phillips said starter Marion Barber will get an increased role in the offense. Another rookie, Tashard Choice, will get some first-team practice repetitions this week.

Jones has 30 carries for 266 yards with three touchdowns. He is third among rookies in rushing yards. His absence hampers the special teams unit. Jones was second in the NFC in kick returns with a 27.1 average and had a 98-yard return for a touchdown.