Here are some initial thoughts on the signings:
Where does Graham fit? Among the Bills' needs in free agency, cornerback was lower on the list. The Bills ended last season with their top trio basically set: Stephon Gilmore and Leodis McKelvin on the outside, with Nickell Robey in the slot. Ron Brooks served as the fourth cornerback and if the Bills were to upgrade, that's where it would be. With Graham's signing, Brooks moves further down the depth chart, while Graham's exact fit among the rest of the personnel remains to be seen.
Graham provides good value: According to ESPN NFL Insider Adam Caplan, Graham's deal will pay him $16 million over four seasons. CBS Sports' Jason La Canfora reported that incentives could push the deal as high as $19 million. On the surface, that's a lot for a potential backup cornerback, but not necessarily when considering other factors. The NFL continues to trend toward more of a passing league, forcing defenses into more sub packages. That could put Graham (and Robey) on the field more than some other "starters" on defense.
Upgrade on special teams: Finally, Graham adds a presence on special teams where the Bills badly needed it. Graham is known as a strong special-teams player -- he represented the NFC in the Pro Bowl following the 2011 season -- and he will join Marcus Easley as the top contributors on that unit. While Graham might not have much of an impact on first or second down, he could earn his money on third and fourth downs, and that's just as important.
Rivers' deal points to scheme change: The Bills added Keith Rivers, a former first-round pick, on a low-money deal. According to ESPN Miami Dolphins reporter James Walker, Rivers is set to earn $5 million over two years. Rivers probably wasn't going to return to the New York Giants, where he started eight games last season. The former first-round pick never panned out with the Cincinnati Bengals, but the Bills have a need at linebacker. There are plenty of moving parts to be sorted out, but Rivers' best shot at landing a starting job would be at strongside linebacker. That's a spot where the Bills could use help -- Manny Lawson may not be a good fit in a 4-3 scheme -- and Rivers is one option to fill that gap.