The Raiders placed rookie CB Chimdi Chekwa on injured reserve and signed former Cowboys DB Bryan McCann.
Chekwa played in four games this season, recording eight tackles and two passes defensed. He hadn't played since Week Four.
McCann has played in five games this season — three for the Ravens and two for the Cowboys. In nine games with the Cowboys as a rookie in 2010, McCann had a 101-yard interception return for a touchdown.