If Sherman loses Friday's appeal, he would be out Sunday vs. San Francisco. However, there is no indication of when a decision might be rendered.
Sherman's suspension stems from a positive test for performance-enhancing drugs. Sources have told ESPN that Sherman tested positive for Adderall.
Fellow Seahawks cornerback Brandon Browner also tested positive but decided to drop his appeal. He began his four-game suspension last week, making him eligible to return for the first round of the playoffs, should Seattle get in.
Any suspension for Sherman would take effect this season and carry into the playoffs, and into the 2013 season, if necessary.
The Seahawks also got a player back from suspension as rookie safety Winston Guy was reinstated after missing the past four games for his own violation of the league's policy on performance-enhancing substances.
Information from The Associated Press was used in this report.