FOXBOROUGH, Mass. --- The New England Patriots have come back from injuries before, winning three Super Bowls and reaching a fourth despite losing Rodney Harrison, Richard Seymour, Junior Seau and Drew Bledsoe.

Now they will try to do it without Tom Brady.

The 2007 NFL Most Valuable Player will miss the entire '08 season with a left knee injury that needs surgery, the team said Monday. That leaves the Patriots without one of the game's great quarterbacks and severely damages their hopes of a return trip to the Super Bowl.

Coach Bill Belichick would not say what the injury is, but the play, Brady's reaction and the prognosis all point toward a torn anterior cruciate ligament.

"As a team we all just have to do our jobs. That really doesn't change," Belichick said Monday, a day after Brady's knee collapsed under him when he was hit by Chiefs safety Bernard Pollard in a 17-10 victory over Kansas City. "He played one position, he played it very well. We have somebody else playing that position now."

The Patriots issued a one-paragraph statement that the two-time Super Bowl MVP will have surgery and be placed on injured reserve. That leaves them in the hands of a backup who's barely been tested.

Matt Cassel, who guided New England to its 20th consecutive regular-season victory after Brady was hurt, will start Sunday at the New York Jets. It will be the first meaningful start since high school for Cassel, who backed up Heisman Trophy winners Carson Palmer and Matt Leinart at Southern Cal and spent the past three years holding a clipboard for Brady.

"I'm not trying to be Tom Brady. I'm just trying to be Matt Cassel," he said when subbing for Brady on his regular weekly radio show. "I don't know where that's going to take us."

Brady led the Patriots to a perfect record in the regular season last year before a loss in the Super Bowl to the New York Giants deprived them of a fourth championship and an unprecedented 19-0 season. They had been favored to return.

"We're not going to tank it the rest of the season. That's not going to happen," defensive lineman Richard Seymour said in a somber and nearly empty Patriots locker room. Seymour was across from where Brady's locker remained stocked with equipment and personal items. "There's always a way to win. We're not going to have a lot of excuses about it."