Johnson was claimed off waivers by the Chargers on Monday, Michael Gehlken of the San Diego Union-Tribune reports.
After losing Branden Oliver to an Achilles injury during Sunday's preseason game to the Vikings, the Chargers moved quickly to replace their No. 3 RB, scooping up Johnson off waivers. A practice squad player with the Cowboys throughout much of last season, Johnson will provide depth at the running back position and could compete with undrafted free agents Dreamius Smith and Kenneth Farrow for the backup job behind starter Melvin Gordon, and pass-catching threat Danny Woodhead.