If this Safety, Mel Mitchell, is healthy and returns to form, I suspect this has a major impact on STs. And on the LB roster, too. An additional ST, nominal DB, may take a position from a ST, nominal LB.
I feel pretty confident that Willie Andrews has already earned a spot on the roster for his ST coverage, and also return, ability. He looks to be a 10 year ST player. If Mel can become the Jerod Cherry of the STs, as he was for the Saints, that can push another STer, off of the team.
That has a couple of ramifications for what appears to be transpiring at LB. Pierre Woods appears to be "getting it". Great news but what that probably means is that Chad Brown becomes a more certain candidate for the "Shadow Roster". Pierre a good ST also, becomes the legitimate #6 LB and the practical 3rd or 4th OLB. This frees an OLB, either Vrabel or AD, to join and take snaps at ILB. This creates a pushdown stack at ILB as well.
The Pats end up with a OLB crew of Colvin, Vrabel, AD and Woods. Don't forget Bruschii and Seau were also OLBs at earlier points in their careers, as well, for emergencies.
They end up with a ILB team of Bruschi, Seau, and swingsters of Vrabel and AD. More than likely they need to keep a couple of ILBs, and guys who can do both play ILB and also ST, if only 8 LBs are kept to make room for the extra DB. Alexander is a ST Maven and played ILB and OLB; Mays did well as a ST player too he is a ILB. Lua might display similar ability as a pure ILB. All are young, and Alexander has taken regular D, ILB snaps. Lua might be in that category too, and Mays is a question mark, but certainly an above average ST player. If two of these three guys prove out, that is a good ST and some regular D ability as well, there is no room for ... Larry Izzo, on an 8 man LB corps.