The Chargers (8-7), who have been eliminated from playoff contention, signed running back Curtis Brinkley and linebacker Darry Beckwith from the practice squad to fill the roster spots.
Tolbert, a third-year pro out of Coastal Carolina, started four of the 15 games in which he played this season, running for 735 yards and 11 touchdowns on 182 carries and catching 25 passes for 216 yards. He sustained a neck sprain during last week's loss to the Cincinnati Bengals.
Tolbert reached 100 yards three times, gaining 100 on 16 carries in Week 4 against the Arizona Cardinals, 111 on 25 carries in Week 11 against the Broncos and 103 on 26 rushes in Week 12 against the Indianapolis Colts. He scored touchdowns in all three games, all of them one-sided Chargers victories.
Cooper, an eighth-year pro and fourth-year starter for the Chargers, has 43 tackles and one sack in 12 games this season. He has a knee injury.
Fullback Jacob Hester (knee), wide receiver Patrick Crayton (wrist) and linebacker Larry English (foot) are doubtful for Sunday's game after missing practice Friday. Center Scott Mruczkowski (ankle) is questionable, and wide receiver Malcom Floyd (hamstring) and linebackers Antwan Applewhite (ankle) and Brandon Siler (ribs) are probable.
The Associated Press contributed to this report.