I've had a few questions about when to draft your team defense. The answer is the second to last round, just before you get your kicker. Especially this year.
I HIGHLY recommend AGAINST drafting a defense early! (especially as early as 8 or 9).
Did you know that in the last 6 years, only 2 "consistently" projected top 10 FF defenses actually finished in the top ten at the end of the year? Only Chicago & Baltimore a few years back. And that was when there was a definite separation in tiers. There is absolutely no clear cut #1 fantasy defense this year.
I especially recommend against reaching for your favorite in round 8, 9 or 10. Some of the absolute best values in the draft this year in those rounds. Not only in IDP where you should be grabbing your top DEs first because there are so few of them. (J. allen, T. Cole, J. Peppers, Tuck, Will Smith), but the offensive side of the ball is HUGE at that point.
Guys like Mike Wallace, Malcom Floyd, Clinton Portis, Marion Barber, Zack Miller, Derrick Mason, Jabar Gaffney, Bernard Barrian, Justin Forsett, Owen Daniels, Brett Farve, Vincent Jackson, Caddy Williams.
Definitely wait on a team defense. Just grab the Browns who play TB week 1 and you'll do great. Or grab the Cardinals who play St. Louis week 1 and you'll do awesome. (Not to mention the fact that the Cardinals have some really crappy teams in their division. As do the Chargers.). How about Tennessee who opens up against Oakland. You get the point. Just play the matchups each week and you'll do great!