Justin Simmons
Among all the free agents on this list, Justin Simmons is the one who would make the biggest impact on the Buffalo Bills. The other players could help the team but they have more questions than being the answer.
As for Simmons, he has either been a second-team All-Pro or a Pro Bowler in each of the past five seasons. During this stretch, he has had 23 interceptions and 36 passes defended and even at 31 years old he is still playing really good football.
The Bills this offseason have done a good job of giving themselves options at safety with re-signing Taylor Rapp, adding free agent Mike Edwards and then drafting Cole Bishop in the second round.
However, Simmons is the best of this group, and a veteran like that in this secondary can help the transition from Jordan Poyer and Micah Hyde. It would also take some pressure off Bishop as the Bills won't necessarily be forced to start early and can give him time to develop.