Now it's time to take the Buffalo Bills seriously in the AFC East.

The last-place Bills, who finished 6-10 in 2011, signed the best player in free agency not named Peyton Manning on Thursday. Buffalo agreed to a whopping six-year, $100 million contract with two-time Pro Bowl defensive end Mario Williams. The contract also includes $50 million guaranteed.

Buffalo general manager Buddy Nix said the traditionally frugal Bills would spend this year in free agency -- and he wasn't kidding. Williams just became the highest-paid player in franchise history.

This is not just a great move for Buffalo. It's potentially a game-changer and home run for this rebuilding franchise, which hasn't made the playoffs since 1999 and hasn't won a playoff game since 1995. Buffalo had a long way to climb to catch the reigning AFC champion New England Patriots in the division. Williams moves the Bills closer to contention.

The trio of Williams, Marcell Dareus and a healthy Kyle Williams gives Buffalo one of the league's most dominant defensive lines. It's a lot easier to win games when you're controlling the line of scrimmage.

Mario Williams, who has 53 sacks in six seasons, brings a much-needed pass rush to Buffalo's new 4-3 defense. Dareus and Kyle Williams are stout, and will make it hard for opponents to run up the middle. This is a bad day in general for quarterbacks and offensive linemen in the AFC East.

With the Patriots and New York Jets relatively quiet so far, and the Miami Dolphins trading away their best player (Brandon Marshall) and possibly falling behind in the Manning sweepstakes, the Bills made up ground with one humongous signing.

How far can Williams take Buffalo next season? It's too early to say. Williams is a huge cog, but questions still remain on the roster.

Can the Bills find a shutdown cornerback? Can they get a left tackle to protect quarterback Ryan Fitzpatrick? Can Buffalo add another receiver to complement Steve Johnson? The draft and the remainder of free agency are important to fill these needs. Buffalo also needs to stay healthy next season.

But the Bills accomplished priority No. 1 this offseason. They needed someone who can get to the quarterback, and landed the top pass-rusher on the market.

That makes Buffalo one of the early winners in free agency.