SANTA CLARA, Calif. — The San Francisco 49ers signed running back DeShaun Foster, quarterback J.T. O'Sullivan and linebacker Dontarrious Thomas today.

Foster spent his first five seasons with the Carolina Panthers, rushing for 3,336 yards and 10 touchdowns in 63 games. The former second-round pick from UCLA will be a backup to Frank Gore in San Francisco, and provides depth for coach Mike Nolan.

O'Sullivan has been with six NFL teams over six seasons. He has appeared in just six games, including five last season with the Detroit Lions under offensive coordinator Mike Martz, who joined San Francisco for the 2008 season.

Thomas has been with the Minnesota Vikings for his first four NFL seasons, making 145 tackles and 1 1/2 sacks. He'll likely be a backup in San Francisco's 3-4 defense.