The Dallas Cowboys are promoting running back Dalvin Cook from the practice squad, adding another option for the NFL’s least effective rushing offense as they prepare for a prime-time game against the rival San Francisco 49ers.

Cook joined the Cowboys late in the preseason but has not played in the first six games. The Cowboys’ running back rotation has been led by Rico Dowdle and Ezekiel Elliott, who returned to the team after being a two-time rushing champion.

A knee injury that ended tight end John Stephens’ season during practice this week allowed Cook to move up from the practice squad.

Dallas placed Stephens on injured reserve on Saturday, which opened a spot on the 53-man roster for cornerback Amani Oruwariye. Oruwariye had been promoted from the practice squad the maximum three times in the last three games.

Dallas (3-3) has only had a strong running game once, during the second half of a win against Pittsburgh. The Cowboys are averaging just 77 rushing yards per game heading into Sunday night’s matchup against the 49ers (3-4).

Dowdle has 246 yards on 59 carries, while Elliott is averaging only 3 yards per carry (38 carries for 115 yards) and has the only rushing touchdown among running backs.

Cook, who was a four-time Pro Bowler in Minnesota, signed with the New York Jets last year after the Vikings let him go. He played a limited role in New York before being released late in the season and appeared in one of two playoff games for Baltimore last year.

After joining the Cowboys, Cook mentioned he wasn’t interested in talking about his confusing time in New York. Earlier this season, he expressed satisfaction with the communication from the Dallas coaching staff.