Cincinnati depends on a dominant defense to win games. There are a number of reasons to believe that our defense may not be as effective as it was last year:
1. Geno Atkins, arguably our best defender, is coming off an ACL injury. While Adrian Peterson and Jamaal Charles (and our own Giovani Bernard) have recovered to be seemingly just as effective as before their injuries, one cannot take Atkins' return to form for granted. Not too long ago ACL injuries used to end careers.
2. The loss of Mike Zimmer. Paul Guenther seems to be up to the task and will probably be an above average defensive coordinator. But Zimmer was something special both in terms of strategy and his connection with players.
3. Leon Hall may be done as an elite corner. Achilles injuries are perhaps worse than ACL tears. Hall has had two of them and will turn 30 next year. After him, we really don't have any stars in the secondary (unless, maybe, Dre Kirkpatrick has a breakout year).
4. The loss of Michael Johnson. While he may not have totaled a lot of sacks last year, he did have 9 passes defended. If Margus Hunt isn't ready to fill his shoes, we may not be able to get as much pressure on opposing QB's, meaning our secondary may end up being exposed to a greater degree.
Meanwhile, on offense, there are the issues of Dalton's contract (and potential departure), a potential lack of depth on the offensive line (with the loss of Anthony Collins) and the lack (so far) of a workhorse back-- Giovani Bernard has looked brilliant at times, but the Bengals didn't feel comfortable with the idea of him being an every down back. That sentiment could continue this year as well (due mostly to his size, and perhaps somewhat as a result of an ACL injury suffered in college). Meanwhile, BenJarvus Green-Ellis turns 29 in July and averaged only 3.4 yards per carry.
To be fair, I might add that the Bengals have been brilliant in the draft in recent years. They may address DE, CB, RB and QB issues this May. But it is still worth entertaining the notion that recent departures and injuries and the lack of moves to compensate for them may catch up with us.