Seattle made the roster moves on Wednesday. Coach Pete Carroll had indicated on Tuesday that Shead would be promoted from the practice squad to the active roster, but waiving Cox came as a surprise.
Seattle signed Cox on Tuesday after cornerback Walter Thurmond was suspended four games for violating the league's substance abuse policy. Cox started the season with San Francisco, but was waived by the 49ers in early November.
Shead was on the Seahawks 53-man roster at the end of last season but was never active for any games. He's spent this entire season on Seattle's practice squad.
"It's a bigger deal to everybody else than it is for me," Maxwell said Wednesday. "I prepare for every game like I'm starting. It's a regular week and you focus on what you need to do. I try to be physical out there and have fun."
Thurmond was starting for Brandon Browner, who has appealed a potential one-year suspension for violating the NFL's substance-abuse policy.
Information from ESPN Seahawks reporter Terry Blount and The Associated Press was used in this report.