On September 9th, the Eagles will face their first opponent of the season, the Washington Redskins. Redskins defensive coordinator Jim Haslett is trying to be as ready as he can be, and has been watching a lot of what Chip Kelly ran at Oregon. From Mark Maske of The Washington Post:
"We've looked at endless film on Oregon," Haslett said. "It's a little bit different because they do some things in college they can't do up here. But it's basically the same, what we saw on film last week [in the Eagles' preseason opener]. I think Chip will do a great job there because they've got great skill players on offense. ... So I think they'll be successful in what they do and how they do it. But hopefully we'll play well in that first game."
I would suspect that the Redskins will be prepared for a lot of the things the Eagles will do Week 1. Clearly, there's some worry there.
However, teams like the Chargers, Chiefs, and Broncos (the Eagles' Week 2, 3, and 4 opponents) don't have the same luxury of preparing this far out for a team that isn't even in their conference. It will be much harder for them to devise a game plan on a whole new offense, in just a week.