Harris joins Mike Davis and Shaun Draughn as the three running backs that will be active for the 49ers when they play the Tampa Bay Buccaneers on Sunday at Levi's Stadium. Starting running back Carlos Hyde has been ruled out with a shoulder injury that he suffered against the Buffalo Bills. The injury is not expected to be a long-term one and Hyde said that he expects to return following the bye week.
Hyde has 429 yards on 109 carries and six touchdowns so far this season. He has averaged 3.9 yards per carry.
Harris has been on and off the roster this season, last being re-signed to the practice squad on October 3. He did not make the team's final roster in September and has been released and signed twice since then. Initially, Harris was a late-season addition by the 49ers in 2015. He rushed for 140 yards on 27 carries in the final two games of the season.
The 49ers had claimed Hart off waivers from the Philadelphia Eagles on September 5. He appeared in one game this season and had two tackles.