According to CBS Sportsline with all the injuries to Seahawks receivers Seneca might get a chance to play:
News: Seahawks coach Mike Holmgren said dynamic backup quarterback Seneca Wallace, who fair caught two punts for Burleson late in the loss to the Bills, "quite possibly" will have a primary receiving role against the 49ers. The club has lost Nate Burleson and Ben Obomanu to season-ending injuries and are without Bobby Engram and Deion Branch for their Week 2 game.
Analysis: As a receiver, Wallace wouldn't be expected to post a ton of stats, though it would certainly be interesting if he played there. Unless he garnered regular playing time, Wallace isn't worth adding to your Fantasy roster for now. He is and will remain QB-eligible in CBSSports.com leagues.