Schilling started just two games in four seasons since the San Diego Chargers drafted him in 2011, both times at guard. Schilling, who grew up in nearby Bellevue, Washington, has appeared in 22 games during his career.
Unger sprained his foot in Monday night's 27-17 victory over the Washington Redskins. After initially being ruled out, Unger missed just three plays before returning to the field to finish the game.
Unger hasn't practiced this week, and coach Pete Carroll said it would require ''a miraculous recovery'' for him to play Sunday.
Safety Kam Chancellor is questionable with a hip injury and will be a game-time decision.
Chancellor missed practice the last two days with what was erroneously listed as an ankle injury. Carroll said he didn't think the hip issue is related to the injury that forced Chancellor to have surgery in the offseason.
Jeron Johnson would start in Chancellor's place if he's unable to play Sunday. Chancellor has missed just one game in his career because of injury.
Percy Harvin returned to full participation in practice Friday after sitting out Thursday with a thigh injury. Harvin is listed as probable.
Tight end Zach Miller will miss a second straight game after ankle surgery.