Free agent Defensive end Mario Williams signed a six-year, $96 million deal ($50 million guaranteed) with the Buffalo Bills, according to Albert Breer of the NFL Network, with potential for the deal to reach $100 million.

The deal is the richest for a defensive player in NFL history. And, only Detroit Lions wide receiver Calvin Johnson's $60 million guarantee from his recent megadeal surpasses that of Williams's as the most in NFL history.

The Bills and Williams have spoken for the past three days since the start of free agency on Tuesday. In that span, Williams has dined with team management and coaches at a downtown Buffalo restaurant and toured the region and the Bills facility.

With Williams, not only could the Bills' pass rush become greatly improved, but it could perhaps become the most formidable defense in the AFC East after it just managed just 29 sacks last season. However, that will hinge on Williams staying healthy. He was limited to just five games last season as a result of a torn chest muscle and missed three games in 2010 after having surgery to repair a sports hernia.

Williams, selected first overall in the 2006 draft by Houston, is a two-time Pro Bowler. He had a franchise-best 53 sacks in six seasons with the Texans, setting a single-season team record with 14 sacks in 2007.