Ryan obviously knows Buffalo and the AFC East well from his time as head coach of the New York Jets. If Ryan becomes the next head coach of the Bills, he'd inherit one of the top defenses in the league. Ryan has traditionally run a 3-4 defense, but he may want to keep Jim Schwartz as the team's defensive coordinator and have them run out of the 4-3. Ryan could also run a hybrid defense.
However, that's talk for a different day. There's no guarantee that Ryan becomes Buffalo's next head coach, but he's the first to get a second interview with the team.
UPDATE: Kimberly Jones, an NFL Network reporter, said that Rex Ryan's second interview with the Bills will last into tomorrow.
"Sounds like the Bills are putting on full-court press with Rex Ryan. Second interview, in Florida, will last into tomorrow."
Perhaps the Bills and Ryan will use that time to hammer out a tentative agreement. Stay tuned as things are getting interesting with the Bills' coaching search.