Yes, I am, especially with potentially high-powered offences coming up in Indy, Cincy and San Diego (twice). I think it's too much to ask for the defence to hold those teams to 10 points or less. Hopefully, Denver is just doing enough to win right now, given they're playing really bad teams, and they can throw a few big plays in the next few weeks. That's a pretty dangerous game to play.
Or, maybe the defence CAN hold anyone they want under 10 points, who knows. But yes, I'm a bit worried right now.