I've always felt that even if you own the Ravens, you cannot start the same defense every week. You have to play the matchups. I always reserve two spots for defense, and at times have kept three defenses on my roster. This year, I have started:
1: Jacksonville vs Buffalo
2: Cincy vs Miami
3: Atlanta vs Arizona
4: Atlanta vs Carolina
5: Atlanta vs Detroit
and haven't had a bad week defensively yet.
Other than Atlanta vs Detroit in week 5 (had to keep starting the hot D), I picked a matchup against an offense which was not only bad, but also *predictably* bad. For instance, although Atlanta's offense has not been great this year, I won't gamble and start a defense against Michael Vick who can be unstoppable when he's on his game. This week, I'm looking at Chicago against Washington. Chicago is always underrated defensively, and Washington has absolutely no offensive line. Washington could be a decent play too, but the safer play is the Chicago D/ST. Offensively, Chicago is a little bit of unknown quantity right now with a totally new offensive scheme, an unknown QB, a new RB. Sounds alot like Washington, but IMO Chicago is less predictable offensively.