As first reported by NFL.com, the fourth-year pro will accept the penalty for reportedly violating the league's non-performance-enhancing drug policy.
Thurmond was a fourth-round draft pick in 2010 by Seattle. He's battled injury problems during his career, although he stepped into a starting role in 2011 before a season-ending injury and again this season with the loss of Pro Bowl cornerback Brandon Browner to a groin injury.
Now the Seahawks' "Legion of Boom" secondary, which has helped the team to a 10-1 record, will be depleted entering the last third of the season that features games against top contenders in NFC rivals San Francisco and New Orleans, which is 9-2 and vying for home-field advantage.
Thurmond, who will be a free agent after this season, has 31 tackles, six passes defended, one sack and an interception, which he returned for a touchdown.