The Raiders released defensive tackle Jay Alford on Tuesday to make room for Davis.
Davis gives the Raiders depth at outside linebacker after starter Quentin Groves hurt his hamstring and backup Thomas Howard injured his knee last weekend against the Houston Texans. Ricky Brown missed the game with a hamstring injury, and rookie Travis Goethel has been out all season with a bad back.
Davis was a third-round draft pick by the Pittsburgh Steelers in 2008 and played in five games as a rookie. He spent part of last season on the New England Patriots' practice squad and was signed by the 49ers last month.
The Raiders also waived cornerback Joey Thomas from injured reserve.
Copyright 2010 by The Associated Press