Running backs Rashad Penny (hamstring) and Travis Homer (calf) and guard Damien Lewis (elbow) were inactive for the Seahawks, who lost cornerback Tre Brown to a season-ending knee injury in their loss last week to the Arizona Cardinals. Alex Collins and DeeJay Dallas were Seattle's only healthy running backs.
To make room on the 53-man roster for Thomas, Washington put rookie right tackle Sam Cosmi on injured reserve with a hip injury. Veteran Cornelius Lucas continues to start in Cosmi's spot.
With starting center Chase Roullier on IR because of a leg injury and backup Tyler Larsen inactive because of a knee injury, natural guard Wes Schweitzer moved to the middle of the offensive line just as he did in Washington's win at Carolina.