Stephan Savoia, Associated Press
New England coach Bill Belichick confers with quarterback Tom Brady during a team practice.

PHOENIX — They are the leaders of a team poised to become the NFL's first undefeated champion in 35 years, and they couldn't be more different — at first glance, anyway.

Tom Brady, 30, is the glamour quarterback from central casting: magnetic and affable, dates supermodels, a GQ cover boy.

Bill Belichick, 55, the coach, is known for his icy glares to the point that he shocks people when he smiles in public. He is anti-glamorous, preferring sweatshirts with cut-off sleeves.

Yet Brady and Belichick are so much alike. Their obsession for perfection has lifted the New England Patriots — a middle-tier team less than a decade ago — to an unprecedented 18-0 record this year. If the Patriots beat the New York Giants in Super Bowl XLII on Sunday, Brady and Belichick will make NFL history, matching the Pittsburgh Steelers' quarterback-coach tandem during the 1970s, Terry Bradshaw and Chuck Noll, for the most Super Bowl titles with four. The San Francisco 49ers' Joe Montana is the only other quarterback with four Super Bowl titles, all in the 1980s.

Much of the focus has been on whether the upstart Giants (13-6) can stop Brady and the game's most explosive offense from capping a perfect season that would top even the 17-0 record of the Miami Dolphins in 1972. Beyond that, however, Sunday's game is perhaps the ultimate test for a behind-the-scenes partnership between Brady and Belichick that has been forged by a dedication to detail and a meshing of seemingly diverse personalities.

They're like "Bogey and Bacall," says Pro Football Hall of Fame quarterback Troy Aikman, a three-time Super Bowl winner with the Dallas Cowboys, comparing Belichick and Brady with Hollywood legends Humphrey Bogart and Lauren Bacall. "A pretty tough combo."

Belichick, not known for doling out praise, says he appreciates Brady's work ethic, competitiveness, passion and leadership. That's also how Brady describes his boss.

"When we sit down, it's not a lot of BS," Brady says. "It's, 'How are we going to win this game?' You have a finite number of minutes between games. You don't want to waste any of those minutes on things that are not going to be so important as winning. So our relationship is based on doing what's best for the team. That's why we get along so well."

The Patriots, favored by 12 points Sunday, are shooting for their fourth Super Bowl title in seven seasons, which would be a run topped only by the Noll-Bradshaw Steelers' four titles in six seasons (1974-75 and 1978-79).

The Belichick-Brady Patriots, however, have created a dynasty at a time when NFL rules — namely a salary cap for each team and a free agency system — are designed to enhance competition and prevent such dynasties.

Since 2000, when Belichick succeeded Pete Carroll and Brady was a sixth-round draft choice, the coach and quarterback have grown into Hall of Fame-bound forces. Brady, a two-time Super Bowl MVP, won three league championships before turning 28 and this season set the NFL record for touchdown passes with 50. Belichick ranks second all time to Green Bay Packers legend Vince Lombardi for postseason winning percentage (.833) among coaches with at least six playoff victories.

Patriots owner Bob Kraft says the root of his team's success is the Belichick-Brady partnership.

"You're not going to get Bill's respect unless you can really produce and also be a great student of the game," Kraft says. "Tommy's work ethic is tremendous, and the way he looks at having a coach like Bill makes it a great fit."

When Kraft, a longtime Patriots season ticketholder, bought the team for $172 million in 1994, the team had never won a home playoff game. Yet after his relationship with then-coach Bill Parcells fizzled and a three-year stint with Carroll bombed, Kraft gave up a first-round pick to the New York Jets to secure Belichick — a move he calls "the best deal of my life."

In his first draft, Belichick picked Brady, a University of Michigan star.

In 2001, Brady became the starter in Week 3 after Drew Bledsoe suffered a severe chest injury.

Bledsoe never got his job back, and Brady began writing his legend by guiding the Patriots to a last-minute field goal that capped a dramatic upset of the 14-point favorite St. Louis Rams in Super Bowl XXXVI.

Who is more essential for success, a coach or a quarterback?

Montana, Brady's childhood idol, might have never won four Super Bowls if he had not landed with the 49ers and Bill Walsh, whose offense was built on timing, short passes and precise reads. Montana never advanced past the AFC title game while finishing his career with the Kansas City Chiefs.

John Elway concluded his career with back-to-back Super Bowl victories with the Denver Broncos after the 1997 and '98 seasons, but he didn't win a title until Mike Shanahan became his coach. Elway was on the losing end of three Super Bowls before Shanahan arrived in 1995. In nine seasons without Elway, Shanahan has one playoff victory.

Belichick's career, which includes five seasons with the Cleveland Browns, further reflects how good coaches and good quarterbacks need each other. Without Brady, Belichick was 42-58, including postseason. With Brady, he's 100-26.

Aikman looks at Belichick and Brady and recalls, wistfully, his relationship with Jimmy Johnson, who led Aikman and the Cowboys to Super Bowl titles in the 1992 and '93 seasons. Aikman won a third Super Bowl with Dallas under Barry Switzer after Johnson left in March 1994 amid a feud with Cowboys owner Jerry Jones, but the victory came amid tension in the coach-quarterback relationship.

Aikman grew frustrated with Switzer's laid-back style, a contrast to Johnson's demanding methods. Since Switzer coached a Cowboys team put together by Johnson to a Super Bowl title in 1995, Dallas hasn't been to another Super Bowl.

Belichick and Brady "have what we failed to keep," says Aikman, who will call Sunday's game as an analyst for Fox.

"Our success in Dallas happened so early that the key people at that time never appreciated what it was that we had. Had we gone through a little different period — maybe if Jimmy had coached in Cleveland for a few years before he got to Dallas — maybe all of a sudden he and Jerry are looking at that thing a little differently and saying, "We have a chance to be really special here. Let's keep this thing going as long as we can."'

Despite the embarrassing blemish on Belichick's reputation stemming from the so-called "Spygate" episode at the start of the season — he was fined $500,000 and the team was docked $250,000 and a first-round draft pick by NFL Commissioner Roger Goodell for secretly videotaping sideline signals by Jets coaches — Kraft signed him last fall to a contract extension of undisclosed value that ties him to the Patriots through 2013. Brady, averaging $10 million a year, is signed through 2010.

The contracts mean Belichick and Brady are likely to remain in their crucial roles for the Patriots even as other parts of the organization inevitably come and go. Just 10 players remain from New England's 2001 championship team, and the winning has continued despite significant losses from Belichick's coaching staff.

During the last three years, offensive coordinator Charlie Weis and defensive coordinators Romeo Crennel and Eric Mangini have left to become head coaches — Weis with Notre Dame, Crennel with the Browns and Mangini with the Jets. Losing such key assistants might cripple some teams, but that has not been true in the Patriots' case.

One reason is Scott Pioli, the team's vice president for personnel and Belichick's right-hand man, groomed by the coach since breaking into the league with the Browns. Pioli heads a personnel department that has been as versatile as the product on the field — scoring major hits with draft picks and veteran free agents alike.

This season, the Patriots have been bolstered by additions including all-pro wide receiver Randy Moss, wide receiver Wes Welker and linebacker Adalius Thomas.

In previous years, linebacker Junior Seau, safety Rodney Harrison and since-retired running back Corey Dillon were added for key roles. Belichick also has been adept at cutting ties with veterans — such as Bledsoe, safety Lawyer Milloy and cornerback Ty Law — who still had NFL mileage remaining but were deemed too costly under the league's annual salary cap ($110 million a team for 2007).

Amid such change, it's easy to overlook Belichick's hands-on impact with Brady.

"One thing most of America does not know is how much Bill Belichick contributes to the offense," says former NFL wide receiver Cris Collinsworth, an analyst for HBO and NBC. "Everybody thinks of him as being a defensive guy. But there is nothing that the Patriots implement that's not Belichick's blueprint. You can ask Tom Brady."

The day after the Patriots qualified for the Super Bowl by defeating the San Diego Chargers in the AFC title game, Brady and Belichick began preparing for the Giants.

As Brady describes it, Belichick breaks down opposing defensive backs in videotape reviews that might last 90 minutes. Before showing the video, Belichick preps his quarterback by discussing the concepts and tendencies he expects from an opponent's defense. Although offensive coordinator Josh McDaniels calls the plays for the Patriots, Belichick doesn't delegate such critical detail work.

"When Tom and I meet, there is no real time frame," Belichick says. "We just go until we get it done.

"To me, there's nothing more important than Tom Brady and nothing more important than what we're talking about. That's indicative of how our relationship's been."

Brady, though, is not pampered.

"Oh, (Belichick) gets on (Brady) like everybody else," Pioli says. "And Tommy doesn't want to be treated differently than anyone else. He never has. That's what's cool about him. And it's one of the ways they are so alike. ... Neither one of them is afraid of being criticized, and they don't have a problem being told they are wrong."

Kraft, feels fortunate that such a relationship exists between his coach and quarterback — and not just because his $172 million investment is now valued at $1.2 billion by Forbes, making the Patriots the third-most valuable NFL team behind the Cowboys and the Washington Redskins.

"The Patriots never really had a great tradition or legacy when we bought the team," Kraft says. "We want to create a legacy where kids 20 years from now feel like Brady feels about Montana, and people feel that way about the Patriots."