Which plays? There was a blown coverage on the TD, a blown assignment on a run and a drop by Tate. Also the 4th and short play was a weak effort. I'm sure that most of the starters aren't quite as focused as they'd be, or should be, come opening day, whereas Seattle is playing guys trying to get a roster spot. This IS their season.
Again, it's entirely possible that this team is no good. But the important part if you're looking for things that matter is more what happens in these joint practices than what we're seeing tonight in vanilla plays with guys that have different motivations.