ARLINGTON — The Cowboys will bring back running back Phillip Tanner for Thursday's preseason final against the Denver Broncos, according to sources.Tanner, who spent the last three seasons with the Cowboys and was recently cut by the Indianapolis Colts, is needed because a plethora of running back injuries. Starter DeMarco Murray and primary backup Lance Dunbar are sitting out the Broncos game for precautionary reasons. Joseph Randle (strained oblique) and Ryan Williams (groin) are nursing injuries and will likely be held out, leaving only running back D. J. Adams available for the game. Adams, however, doesn't know the entire offense after joining the team midway through training camp. Tanner's experience and knowledge of the system made signing him an easy call. The Cowboys will need to make a roster move before officially signing Tanner.