Bills land defensive end Mario Williams

As first reported by FOXSports.com, defensive end Mario Williams agreed Thursday on a multiyear contract.

FOXSports.com NFL insider Jay Glazer reports the deal includes a staggering $50 million guaranteed, making it the largest free-agent contract ever signed by an NFL player. It’s a six-year deal with a maximum value of $100 million.

The deal ends a two-day courtship of Williams that included a trip to Buffalo by his fiancé. Having failed to reach the playoffs since the 1999 season, the Bills made Williams the focus of their free-agent push after re-signing wide receiver Stevie Johnson to a multiyear contract extension on Monday.

Williams is Buffalo’s most dynamic defensive roster acquisition since Smith, the Hall of Fame defensive end who spent the first 15 years of his NFL career (1985 to 1999) with the Bills. Williams also was considered the top defensive player on this year’s free-agent market. The Texans didn’t have enough money under the salary cap to re-sign him to a contract extension.

Williams, 27, was the top pick in the 2006 NFL Draft following his junior season at North Carolina State. He signed a six-year, $54 million-deal and was selected ahead of hyped stars such as Reggie Bush and Vince Young.

Williams started slow during his rookie season, compiling 47 tackles and 4.5 sacks. However, he improved greatly in his second season by racking up 14 sacks along with 59 total tackles.

Williams came into his own in his third season. He lived up to his No. 1 pick reputation and was a first-team All-Pro selection as the anchor of a steadily improving Texans defense. In 2008, he was a first-team All-Pro again and earned the first of back-to-back Pro Bowl selections.

Under new defensive coordinator Wade Phillips, the Texans converted Williams into a hybrid end/outside linebacker for the 2011 season. Williams had five sacks in Houston’s first five games before missing the rest of the year with a torn pectoral muscle.

Williams will now be paired with defensive tackle Marcell Dareus, who had a solid rookie season as the No. 3 overall pick in the 2011 NFL draft, in Buffalo’s front four.