The Seahawks defense is not quite up to par from the 2013 season, IMO.
Their sack numbers are down this year (less than the Patriots defense), they do not have the depth due to key injuries (e.g. Mebane) and departures (Bryant, Clemons etc.), which gave them the luxury of fielding a very effective rotation, allowing the pass rush to come in swarming waves.
They are still very good, and so is their run defense. However, I would still expect the Patriots to test the middle of their defense with dive plays with Blount.
If these are even moderately effective (averaging 2-4 yards consistently), then it opens up play action for Brady to find those soft spots behind the linebackers and in front of the safeties. Of course, it will be crucial that Brady be successful on these opportunities.
All in all, the Seahawks defense is still very good (the best the Pats will face all year), but not quite the same caliber that the Broncos faced in New York a year ago.