The Thursday night game against San Francisco is an NFL Network production. That means you can't watch the game on a local affiliate unless you are living in the Seattle/Tacoma area. KCPQ Channel 13 is carrying the game here, but not in other places where fans have become accustomed to getting the games (Spokane, for one).
That means you'll need NFL Network if you are among the billions of people who do not live in the local market. The league points out that NFL Network is available on DirecTV (channel 212 in Bad Picture and 95 in High Definition); and Dish Network (channel 154 in BP, 9426 in HD). Comcast Cable subscribers in my area can get KCPQ on channels 13 (BP) and 113 (HD).
Note: The Seattle-Arizona game re-airs on NFL Network tomorrow at 10:30 p.m. EST. through the "NFL Replay" show. I will probably watch this just to make sure the Seahawks really did lose a game to the Cardinals even though Matt Hasselbeck finished the game with three touchdowns, no interceptions and a passer rating in the 130s. I'm thinking he might throw a couple of picks in the replay, in which case the defeat would make a little more sense.