WR: Buffalo badly needs a complementary piece for Stevie Johnson. David Nelson had 61 grabs last season — and he'd be a nice fit as a No. 3 WR, as opposed to the No. 2 guy.
OT: The Bills (sort of) committed to Ryan Fitzpatrick last season, and now they need a LT to protect his blindside. Demetress (formerly Demetrius) Bell bailed for Philadelphia, leaving an even bigger void.
LB: Adding Mario Williams and Mark Anderson will crank up Buffalo's QB pressure. Taking a LB who can get into the backfield would add to the Bills' new defensive intimidation.