The Chargers needed an experienced running back to spell second-year pro Melvin Gordon, who has been playing a majority of the reps in the backfield and is on pace for 400 touches this season.
Running backs Danny Woodhead (knee) and Branden Oliver (Achilles) are done for the year, and Dexter McCluster joining them on the injured reserve list three weeks ago after suffering a broken forearm in a freak accident at home.
San Diego gets the change-of-pace runner it needs in Hillman. At 5-foot-10 and 195 pounds, Hillman totaled 1,985 career rushing yards and 12 rushing touchdowns during his four years with the Denver Broncos and five games this season with the Vikings.
The Chargers' signing of Hillman represents a homecoming of sorts for the San Diego State alum.
Hillman, 25, also has 71 career receptions for 474 yards and a score. Holding on to the football has been an issue for Hillman in the NFL, as he has put the ball on the ground eight times, losing three of those.