Obviously numbers three and five...
The Pats will certainly make an effort to retain both Moss and Samuel. And if they fail with either, they will look at the other free agents at those positions.
At WR, Crayton is a huge downgrade from Moss. There is not a comparable receiver out there. The Pats could look at Devery Henderson or Keary Colbert, but those are also complementary guys.
At corner, there are two potential impact players that might become free agents. Marcus Trufant is a very good corner, and there's a chance he will be available. Nnamdi Asomugha is also out there, but he's more likely to be retained. Again, after that, the list drops off dramatically. Randall Gay will be a top ten corner, easily, in this free agent group.
The other area the Pats will need to look for free agents is LB. With Bruschi and Seau likely to retire and Colvin carrying an enormous cap hit, there's a real good chance the Pats will need an overhaul. The options there are not very good right now. If a guy like Taylor is released under a turn-around regime, things could improve, and the Pats could always draft a top prospect, but obviously they prefer veteran free agents.