The National Football League lost one of its most successful and popular players in the first eight minutes of his season opener.

New England Patriots quarterback Tom Brady will miss the rest of the season after the league's reigning Most Valuable Player injured his left knee 7:27 into the team's 17-10 victory over the Kansas City Chiefs two days ago.

Brady, 31, will be replaced in the lineup by reserve Matt Cassel, who hasn't started a game since high school, coach Bill Belichick said.

"It's a blow, no question," said Rick Gentile, director of the Seton Hall University Sports Poll that tracks public attitudes toward the business of sports. "The Patriots might win, but they're just not as attractive a television entity as they once were."

The Patriots said in a news release that Brady's injuries will require surgery, without providing details. Coach Bill Belichick said at a televised news conference that he had no details and that the Patriots had no immediate plans to try out other quarterbacks such as free agents Chris Simms and Daunte Culpepper.

Asked how Brady received the news, Belichick replied: "Probably about like you'd expect."

Brady's injury costs the NFL one of its top players and biggest personalities. He's won three Super Bowl titles in four appearances and earned the championship game's most valuable player trophy twice. He was named the league's MVP last season after throwing a record 50 touchdown passes.

Brady led the Patriots to 18 consecutive wins last season before losing to the New York Giants in the Super Bowl. Along the way, Patriots games set television audience records.

Biggest Audience

The Super Bowl was the most-watched in history, with 94.1 million viewers, according to News Corp.'s Fox unit, and its peak audience of 105.7 million viewers fell just shy of the most-watched telecast ever, the 106 million people who tuned in the finale of "M*A*S*H." The Patriots set audience records while playing in the four highest-rated NFL games.

Brady is also one of the league's most popular players. He ranks third among active football players on Marketing Evaluation Inc.'s Q Scores, which measure U.S. consumer awareness of celebrities and their marketability, behind New York Jets quarterback Brett Favre and Indianapolis Colts quarterback Peyton Manning. Esquire magazine named him the world's best-dressed man in 2007. He dates model Gisele Bundchen, labeled the most beautiful woman in the world by Rolling Stone magazine.

Brady's Ads

Brady has done advertisements for companies including Visa Inc., Nike Inc., Sirius Satellite Radio Inc., Coca-Cola Co.'s Glaceau unit and watchmaker Movado Group Inc. He made about $9 million from endorsements in 2007, according to Sports Illustrated. His base salary with the Patriots this season is $5 million, according to the Boston Globe.

The day before his injury, Brady was featured in newspaper ads for NetJets Inc.

David Carter, executive director of the Sports Business Institute at the University of Southern California, said the NFL has other marketable storylines this season, even without Brady.

"The NFL is blessed with a number of stars," he said. "They don't have all their marketing eggs in one basket."

The Patriots' odds of winning the Super Bowl lengthened after Brady's injury, according to Mike Seba, senior oddsmaker at Las Vegas Sports Consultants, which advises sports books on betting lines. After making New England the preseason favorite with 5-2 odds, Seba reduced the chances to 15-1 yesterday morning.

Cowboys Favored

The Dallas Cowboys are now the favorites, at 4-1, with the San Diego Chargers second at 7-1.

Cassel, a seventh-round draft choice from the University of Southern California, has played in 15 NFL games, completing 35 passes in 57 attempts for 405 yards, three touchdowns and two interceptions. Belichick said the team had "a lot of confidence" in his ability to run the offense.

Cassel, 26, completed 13 of 18 passes for 152 yards and a touchdown as the Patriots beat Kansas City 17-10 two days ago.

"He's capable of handling himself in a lot of different situations," Belichick said. "He showed that yesterday, that he can go out and manage the team and manage the game."