ORCHARD PARK, N.Y. -- New England quarterback Tom Brady might want to watch his back. The Jets' Mark Sanchez, too.
After spending the past six seasons harassing quarterbacks for the Houston Texans, defensive end Mario Williams -- one of the NFL's top pass-rushers -- has found new motivation in a whopping contract and a new home in the AFC East with the Buffalo Bills.
"I'm ecstatic, very excited. I can't wait for the opportunity," Williams said Thursday after signing a six-year deal potentially worth $100 million. "There's no pressure. I've played against great quarterbacks. And I'm looking forward to playing against these quarterbacks, chasing them down and making things happen."
Williams' deal, which includes $50 million in guaranteed money, is the richest ever given to an NFL defensive player. It came after two days of talks, which started when the Bills flew the former top draft pick to Buffalo on a private jet Tuesday, shortly after the NFL's free-agency period opened.
Terms of Williams' contract were provided by the player's agent, Ben Dogra.
"We got a lot better," Buffalo general manager Buddy Nix said, noting the Bills addressed their highest offseason priority by bolstering what had been an anemic pass rush. "Good things come to the people that wait. So you guys have been waiting, and we've got a good thing here."
Though the contract was agreed to shortly after noon, the news conference to introduce Williams was delayed by more than two hours as the two sides worked out the final details.
The wait was even longer for Nix, who noted the Bills' pro scouts identified Williams as their key target since January.
"The No. 1 guy for us from Day 1 was this guy," Nix said. "Obviously, you don't do anything until he hits free agency, but it's been a long process. And it's been fun, especially since it turned out right."
After quarterback Peyton Manning, Williams has been regarded as one of the top free agents available this offseason.
Williams' addition immediately improves a defense that had difficulty applying pressure since Aaron Schobel was released before the 2010 season. Buffalo managed just 27 sacks in 2010, and 29 sacks last season, 10 coming in one game.
Listed at 6 feet 6, 285 pounds, Williams is a two-time Pro Bowl starter and had a franchise-best 53 sacks in six seasons with the Texans. Williams was limited to playing just five games last season as a result of a torn chest muscle. He also missed three games in 2010 after having surgery to repair a sports hernia.
Williams said he's healthy, and is accustomed to the playing in the spotlight.
The Texans initially were questioned for overlooking running back Reggie Bush by drafting Williams with the No. 1 pick in 2006.
"The only pressure and motivation I have is to come in here and do what I need to do with my teammates and for us to succeed," Williams said.
Coach Chan Gailey is looking forward to seeing Williams help a line that features two solid tackles in Kyle Williams and Marcell Dareus.
Kyle Williams is expected to be fully healthy after having surgery to repair a nagging foot injury. Dareus, the third player picked in last year's draft, is coming off a promising rookie season in which he led the Bills with 5½ sacks.
"I can't put a percentage on how much better we are, but I know we're appreciatively better," Gailey said. "A better pass rush makes a better secondary. A better defense makes a better offense. It all works together."
Mario Williams was intrigued by Buffalo, and did his homework after getting the sense the Bills might pursue him in free agency.
In the past few weeks, he spoke to players familiar with the city, and his Texans position coach, Bill Kollar, who spent two seasons with the Bills.
Then he got a chance to learn more about the city over the past two days touring the region, along with his fiance, Erin Marzouki, who arrived in Buffalo on Wednesday. What Williams discovered is that Buffalo reminded him of his small-town home of Richlands, N.C.
"It was just like going back," he said. "I couldn't say no, it's a family atmosphere here."
He immediately noted Bills fans' passion for football, and how many came up with colorful ways to urge Williams to sign with Buffalo. The best example was seeing pictures of a local pizza place using pepperoni to spell out "Come Mario 90" on its pies, the 90 referring to Williams' number in Houston.
The avid outdoorsman, Williams also found a hunting partner in the get-acquainted process, Bills' Hall of Fame quarterback Jim Kelly.
Kelly played a role in the recruiting by inviting Williams and Marzouki over to his house in suburban Buffalo. It was during the visit that Williams happened to spot nine deer in Kelly's backyard.
More important, Williams believes he can make a difference on a team that got off to a 5-2 start last year before unraveling by losing eight of its last 10.
"You saw from the very beginning of last year what is capable here," Williams said. "We're just adding more pieces."
And Williams is a big one.