Free agent defensive end Mark Anderson is on the verge of signing with the Buffalo Bills, according to Alex Marvez of FOXSports.com. Ed. Note: The signing is now official, as the team has announced it. It's a four-year deal worth $27.5 million, with $8 million guaranteed, per Adam Schefter.

Anderson, who will turn 29 in May, is coming off of a 10-sack season with the New England Patriots. The seventh-year pro recorded 12 sacks as a rookie fifth-round pick of the Chicago Bears in 2006, spent three more seasons there, and then recorded four sacks as a sub-package pass rusher with the Houston Texans in 2010. There, he was a teammate of Mario Williams, who signed a six-year, $100 million deal with the Bills just last week.

The 6'4", 255-pound Anderson is expected to compete with Chris Kelsay and Shawne Merriman for the starting right defensive end job opposite Williams. Between Williams and Anderson, the Bills have now guaranteed $58 million to pass rushers this off-season.