The loss of Roddrick Muckelroy is a bummer but the sky isn't falling yet.  I also don't buy the reports that Dan Skuta is the favorite to start in Rey's old SLB position.  Newcomer Thomas Howard would seem to be the logical fit there with Dontay Moch backing him up.  At MLB, obviously Maualuga will start with Skuta and/or Vincent Rey as a backup.  As for WLB, Rivers is the starter on paper but with his injury we'll need a replacement to start the season.  Howard could shift to WLB forcing Skuta to start at SLB (Moch won't be ready) but that's a lot of changes for a team that could use stability and simplicity.  The best solution would be to bring back Brandon Johnson and have him start at WLB for the first six games.  He's filled in for Rivers before and is familiar with Zimmer's defense.  Heck, he participated in 48% of the snaps last year which just barely trailed Rivers' 51%.  Assuming Rivers can return healtht and stay health, Johnson can provide solid depth at both OLB positions and provide a boost to special teams.  The team has the cap room to afford him ($2.5-3.0M/year probably based on the Tulluch, Howard and Ruud deals).

If Skuta is really moving outside for good, I'd suggest getting a "young" veteran to back up Rey.  Kirk Morrision, the high-pitched Abdul Hodge or Ricky Brown are all good options here.