There are two secrets to the Cincinnati Bengals' success on defensive line—one is defensive tackle Geno Atkins, the best player at his position in the league, and the other is the rotational approach they take with the line.
Though this has been a more stable sort of rotation this year, there have been roles in which certain players are better-suited, and that's illustrated best by their use of defensive ends Robert Geathers, Wallace Gilberry and Michael Johnson.
All three split snaps between pass rush and run defense, as makes sense for 4-3 defensive ends, with all three men having more time as pass-rushers than run-stoppers. Johnson had the most playing time of any member of the line, with 870 total snaps—312 against the run, 534 in pass rush and 24 in coverage.
The result has been 52 total tackles, 11.5 sacks (the second-most on the team), an interception and a fumble recovery. Johnson cannot be easily replaced, even with the great number of pass-rush specialists entering this year's draft. He must be retained.
The same can also be said for Geathers and Gilberry. Geathers has three sacks, while Gilberry, who has played only 316 snaps, has 6.5 sacks to his name, as well as a fumble recovery for a touchdown.
Though there may be some push for the Bengals to get younger on the defensive line, that doesn't provide a strong enough argument for them letting any of these proven veterans walk. This is the best defensive line in the league for a reason, and it would be better if it remains intact.