Davis had been on the practice squad for the Chicago Bears before the Raiders signed him to help replace Griffith.
Griffith tore the ACL in his right knee late in the third quarter of a 29-10 loss to Baltimore on Sunday. He stayed in the game for a few plays and managed to score Oakland's only touchdown on a 2-yard catch. He was hit hard by Ray Lewis on the play and knocked out of the game.
The injury left the Raiders with only one healthy fullback, Luke Lawton, who has mostly played special teams after being brought in late in training camp, when Oren O'Neal went down with a season-ending knee injury.
Davis started two years in college at Illinois before spending the 2006 season on injured reserve with Philadelphia with a knee injury. He was on the Eagles' practice squad last season and on the Bears' practice squad this year.
The Raiders also waived offensive lineman Seth Wand, who had been on the injured reserve list with a knee injury.