SAN FRANCISCO -- At long last, running back Dalvin Cook will make his Dallas Cowboys debut Sunday against the 49ers.

Signed to the practice squad a week before the season started, Cook has waited patiently as the Cowboys' running game has sputtered. The Cowboys are averaging 77.2 rushing yards per game, lowest in the NFL, and have gone a franchise-record 20 games without a 100-yard rusher.

On Friday, coach Mike McCarthy said Cook was ready for the opportunity.

In the past few weeks, Cook has seen his snaps with the first team increase. A four-time 1,000-yard rusher with the Minnesota Vikings, his career has stalled recently after gaining 214 yards in 15 games with the New York Jets last year. He appeared in a playoff game for the Baltimore Ravens and had 23 yards.

The elevation from the practice squad brings questions about how the Cowboys will fill out their running back position on game day.

Rico Dowdle leads the Cowboys with 246 yards and Ezekiel Elliott is second with 115 yards, but can the Cowboys dress three running backs who do not play special teams?

They have dressed three running backs in four games, but Deuce Vaughn has been inactive the past two games. Fullback Hunter Luepke has been a staple of the offense and special teams.

Elliott has been a healthy scratch in his career only when he was rested in regular-season finales with the playoffs upcoming.

The Cowboys also placed tight end John Stephens Jr. on injured reserve Saturday after he tore the ACL in his left knee in Wednesday's practice. Cornerback Amani Oruwariye was signed from the practice squad. He was out of elevations after playing in the past three games.