I think Seattle is a veteran team that falls into the trap of pacing themselves too often during the regular season so they have some ugly letdowns especially on the road.
They know they can turn it on for the big games and playoffs. Wilson, for example, has learned not to try to make a big gain every play of the regular season but to wait for playoff time and today IMO he will run a lot more than we have seen. Yes they say he will probably take the knee brace off he has worn all season.
Seattle has a very strong front 7 against both the run and pass and though S Thomas is a big loss their secondary is still top notch. So, a superior D compared to Detroit.
And the Detroit OL is not very good. Stafford's finger in colder weather will be a problem, his rating has dipped a lot last 3 games after the injury and cold weather makes it worse. 2 of his last 3 were in warm weather (Dallas and GB) and the one in NY he only got 7 pts though the Giant D is looking good.
8 is a lot to lay with a team with a weaker offense but Detroit does not have the bodies to push Seattle around and Wilson has some good WR/TE targets.