Very interesting. I think the Seahawks are one of the most physical teams in the league, and if they can get to Manning early and rough up his receivers, it could be a long day. Manning's known weakness are cold, wet, and/or getting hit early in games. They mentioned a stat on NFLN the other day for these categories, and Manning's record is abysmal when teams shake up his routine and knock him around. His record in incremental weather is horrible, as well. Indy's dome treated him well.
Should be a good matchup, because the Seahawks secondary is so good that they can man coverage every position. They'll knock the snot out of Welker if he tries that pick and roll block again. I'd expect they will greet him with a hit just as hard.