Sure, if Kuechly was healthy and available...or Bobby Wagner, maybe.
There are no LBs on the market who have remotely the defensive impact of Suh. Look, I don't much like the guy, but he's a stud DL. Athletically, he's way better than 95% of DLs out there.
There may be other problems, sure, but the guy is a beast. The best remaining linebacker? Zach Brown? Preston Brown? Yeah, Ill take either, or both for that matter, or Bowman if he's not toast, but the only other truly impact players available on D, to me, are Sheldon Richardson and Dontari Poe, and with Shelton in the fold, I don't think Poe fits.