Seahawks CB Walter Thurmond cracked the fibula in his left leg and will miss the rest of the season.
Thurmond suffered the injury in Sunday's loss to the Browns. Rookie Richard Sherman replaced Thurmond in the second half.
Thurmond had stepped in for Marcus Trufant, who was placed on injured reserve. In six games and three starts this season, Thurmond, a second-year player, has 12 tackles and two passes defensed.