Cincinnati's use of the base 4-3 defense (as opposed to say, nickel) was by far the most used Sunday against the Baltimore Ravens, often with your standard three linebackers in Rey Maualuga, Manny Lawson and Thomas Howard along with four members of the secondary. As far as we can tell 52 snaps on defense sported a secondary roster of Nate Clements, Reggie Nelson, Chris Crocker and Adam Jones.
What's more evident is Cincinnati's injuries at defensive end. Michael Johnson missed significant time after suffering an injury against the Ravens that limited him to only 18 snaps on Sunday while Dunlap, already dealing with a hamstring issue, had the lowest snap count on the defensive line last weekend.
(snap count account to Pro Football Focus)