Buchanan was a seventh round draft pick of the New England Patriots in the 2013 NFL draft. In his rookie season, Buchanan played in 15 games and recorded five tackles and two sacks. Buchanan also played in over 40 percent of New England's special teams snaps in 2013. Last season, Buchanan spent the majority of the 2014 season on the injured reserve. He was waived by the Patriots on May 7.
In 2013, Gil Brandt provided the following draft analysis of Buchanan:
"Buchanan had a strong 2011 season, but then former teammate Whitney Mercilus left for the NFL last year, and Buchanan took a bit of a step back. He's got the size, speed and athletic ability to rush the passer."
If signed by the Bills, Buchanan will compete for a roster spot at outside linebacker.