Bills reel in Mario Williams

One of the top free agents is no longer available.

Mario Williams, a pass rusher selected first overall in the 2006 NFL Draft by Houston, agreed to a six-year contract with the Buffalo Bills on Thursday.

The deal is reportedly worth up to $100 million, with $50 million guaranteed.

A two-time Pro Bowl selection, the 6-foot-6 Williams, a defensive end capable of switching to linebacker, was limited to just five games last season as a result of a torn pectoral muscle. He had missed only three games -- all in 2010 after having surgery to repair a sports hernia -- prior to last year's setback.

Williams, 27, posted a Texans' franchise-best 53 career sacks, including a team single-season best 14 in his second year.