The Giants may not have finished celebrating their championship, but they started taking steps toward winning another yesterday when they signed the architect of their Super Bowl-winning defense to a contract extension. Defensive coordinator Steve Spagnuolo, who had appeared close to leaving the Giants to become the head coach of the Washington Redskins, instead yesterday agreed to a new contract to remain at the helm of the Big Blue defense. Although details of the deal have not been disclosed, it is believed to be a three-year contract extension that will pay Spagnuolo more than $2 million a year and make him the highest-paid defensive assistant in the NFL. Based on his first season — and especially his first postseason — running the Giants’ defense, Spagnuolo is worth every penny.

A year ago — or even four months ago — it would have seemed inconceivable that Spagnuolo could be the league’s highest-paid defensive assistant. When head coach Tom Coughlin hired him in January 2007, Spagnuolo had never been a coordinator, and his only NFL experience was as an assistant with the Philadelphia Eagles. Coughlin fired his previous defensive coordinator, Tim Lewis, at the end of last season, just a day after receiving a one-year contract extension.

At that time, Spagnuolo seemed like a solid — but not spectacular — choice to run the defense. But at the start of the 2007 season, even “solid” would have been pushing it. The Giants’ defensive players at first appeared to struggle to figure out Spagnuolo’s schemes, and Spagnuolo needed time to determine the best way to play the hand he’d been dealt. In the Giants’ first game of the regular season, they gave up 45 points in a loss to the Dallas Cowboys. The following week they allowed 35 in a loss to the Green Bay Packers. But the improvements the defense made over the course of the season were evident when the Cowboys and Packers scored just 17 and 20 points when the Giants beat them in the playoffs.

Spagnuolo’s defense is known mostly for blitzing opposing quarterbacks. In the regular season, the Giants led the NFL with 53 sacks, and in Super Bowl XLII, they sacked New England Patriots quarterback Tom Brady five times, the most he had been sacked in one game since 2003. But the Giants were just as effective stopping the run as the pass last season, ranking among the top 10 in the league in rushing yards allowed, rushing yards allowed per carry, and rushing first downs allowed. That’s the sign of a team playing with well-balanced defensive game plans, and it’s also the sign of a team with a defensive line that accomplishes the rare feat of maintaining constant pressure against the pass without losing discipline against the run. For that, both Spagnuolo and Giants defensive line coach Mike Waufle deserve an enormous amount of credit.

Still, Giants fans shouldn’t assume that keeping Spagnuolo means the defense will play as well throughout 2008 as it played on Super Bowl Sunday. The NFL is full of assistant coaches who are labeled geniuses one year and idiots the next. In fact, while Spagnuolo will be the highest-paid defensive coordinator in the NFL this year, the two highest-paid defensive assistants in the NFL last year were Gregg Williams of the Washington Redskins and Dom Capers of the Miami Dolphins. Both Williams and Capers had mixed results in 2007, and both lost their jobs this offseason.

And even if the defense does continue to play the way it played in the Super Bowl, Spagnuolo’s three-year contract doesn’t necessarily mean he will stay for three years. If the Giants remain at or near the top of the league in 2008, Spagnuolo will undoubtedly receive more interest from teams looking to hire him as head coach. Top teams rarely keep their coaching staffs intact for long.

Up next for the Giants will be a contract extension for head coach Tom Coughlin, who has one year remaining on his current deal. That the Giants’ ownership is willing to shell out $2 million a year for an assistant is a very good sign for Coughlin; the salary in his new deal could be in the $5 million a year range.

Coughlin and the team have come a long way since last year, when the Giants began the offseason by giving him a contract extension that made most fans think they were in for another mediocre season. This year, the Giants are beginning the offseason with a contract extension that will make fans dream of another championship. Winning the Super Bowl has a funny way of changing expectations.

Mr. Smith is a writer for FootballOutsiders.com.