This is another sign that the Ravens are confident that cornerback Lardarius Webb (back), who is questionable on the injury report, will play Sunday against the Cincinnati Bengals. The Ravens are down to four cornerbacks without Cox.
The move is likely a procedural one as well. If Cox was on the season-opening roster, his $730,000 salary would have been guaranteed. Now, the Ravens can re-sign Cox as soon as Monday and only be on the hook to pay him for the weeks he is on the roster.
The Ravens didn't announce a corresponding move, but it's expected that a practice-squad player will take Cox's place on the roster. Inside linebacker Josh Bynes, who worked with the team all week as a member of the practice squad, could be a candidate to be promoted to the 53-man roster because of his value on special teams.