Santa Clara, CA (My Sportsbook) - The San Francisco 49ers announced on Wednesday that running back Kevan Barlow has been placed on injured reserve due to his lingering knee injury.

The team also announced the signing of third-year defensive back Kris Richard to fill Barlow's roster spot.

Barlow, who leads the 49ers with 581 rushing yards this season, has been battling through the injury for some time. He missed a Week 13 loss to Arizona before returning to action the next week against Seattle, but managed only 33 yards on 11 attempts.

Barlow hasn't played since the 49ers' 41-3 loss to the Seahawks in Week 14.

Rookie Frank Gore and Maurice Hicks have been handling the bulk of the carries in Barlow's absence. Hicks rushed for 109 yards on 10 carries, scoring on a 73-yard run, in the Niners' 24-20 win over St. Louis last week. Gore had a pair of touchdown runs against the Rams.

Richard was signed to help shore up San Francisco's injury-riddled defensive backfield. Derrick Johnson (stinger), Bruce Thornton (knee), B.J. Tucker (finger), Shawntae Spencer (quad) and Ahmed Plummer (ankle) are each hampered entering the final week of the season.