The Buffalo Bills placed running back C.J. Spiller on injured reserve Tuesday but designated him for return.

To take the place of Spiller and injured Fred Jackson on the roster, the Bills signed free-agent running back Phillip Tanner. Terms of Tanner’s deal were not disclosed by the team.

Spiller sustained a broken collarbone and Jackson injured a groin in the Bills’ 17-16 victory over the Minnesota Vikings on Sunday.

Tanner played in 40 games spanning three seasons for the Dallas Cowboys. The 26-year-old had 149 yards rushing and two touchdowns on 56 carries and nine catches for 93 yards while he was with the Cowboys.

Jackson is expected to be out about four weeks. Spiller’s return is uncertain.

Spiller leads with Bills in rushing this season with 287 yards on 69 carries and Jackson was close behind with 239 yards on 55 carries. Jackson also has 33 receptions for 261 yards and Spiller has caught 14 passes for 109 yards.