As the NFL officially announced Tuesday afternoon Walter Thurmond’s four-game suspension for substance abuse, the Seahawks signed former 49ers CB Perrish Cox, who worked out with the team Monday and passed a physical exam Tuesday, the Seahawks’ first full practice day after a bye week.

The Seahawks were also expected to put CB Brandon Browner on injured reserve with a groin muscle torn in the Atlanta game. That rules him out for the rest of regular season. The NFL is expected to announce a one-year suspension for Browner later this week for multiple violations of the NFL’s policy on substance. That almost certainly ends the Seattle career of Browner, 29, who was scheduled to be a free agent after the season.

Adding Cox, 26, gives Seattle a fourth cornerback for the Monday night game against New Orleans at the Clink. The club also worked out former Seahawk Marcus Trufant Monday, and has been talking to Antoine Winfield, who was cut after training camp when he was beaten out by Thurmond. They also could promote DeShawn Shead from the practice squad. A club can add a players to the roster while others are suspended.

Cox, a fifth-round draft choice in 2010 by the Denver Broncos out of Oklahoma State, has 40 career NFL starts, including nine for the 49ers this season.

Thurmond will be eligible to return for the Seahawks’ final regular-season game against St. Louis, plus the postseason.

Looking forward to the next chapter in my NFL career as a member of the Seattle Seahawks!!! Can’t wait to get back on the field!!#GoHawks

— Perrish Cox (@pcox16) November 26, 2013