CINCINNATI — Bengals safety Dexter Jackson, who has missed most of the season with a thumb injury, has been placed on injured reserve with a hamstring injury suffered in practice.

Jackson missed five of the Bengals' eight games because of the thumb. He returned and played in the last two games, but hurt himself in practice Wednesday. He was placed on injured reserve today.

The Bengals signed free agent safety Chris Crocker, a sixth-year player from Marshall. He started the season with Miami, played in six games and was released on Oct. 21. Crocker has also played for Cleveland and Atlanta.