On Monday, the AFC East blog reported the Buffalo Bills and guard Kraig Urbik were in the process of hammering out a four-year extension.

It turns out that both sides worked into the night and finalized an agreement. A source tells ESPN.com's AFC East blog that Urbik and the Bills agreed to a four-year, $15 million extension.

Urbik is a two-year starter for Buffalo who has the versatility to play both guard spots and center. He is one of the anchors of an offensive line behind which Bills tailback C.J. Spiller recorded his first 1,000-yard season.

The Bills are getting an early start on their 2013 free-agent class. Other Buffalo players who are set to become free agents include starting safety Jairus Byrd and guard Andy Levitre.