FOXBOROUGH, Mass. -- Tom Brady will miss the entire season with a left knee injury that needs surgery, leaving the New England Patriots without one of the game's great quarterbacks and severely damaging their hopes of a return trip to the Super Bowl.
The 2007 NFL Most Valuable Player will be placed on injured reserve, the Patriots said Monday, one day after Brady's knee collapsed under him when he was hit by Chiefs safety Bernard Pollard in the first quarter of a 17-10 victory over Kansas City.
"As a team we all just have to do our jobs. That really doesn't change," New England coach Bill Belichick said. "He played one position, he played it very well. We have somebody else playing that position now."
A one-paragraph statement issued by the team confirmed that the two-time Super Bowl MVP will have surgery, ending a 128-game starting streak that is the third longest for a quarterback in league history. 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.
Brady sounded optimistic about the Patriots in an e-mail to NBCSports.com.
"It will all be OK," he wrote. "I'm excited to see what our team is made of ... I still like our chances."
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 California 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 took the Patriots to three NFL titles since 2001 and led them 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 -- before Brady's injury.
"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 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."
Even without Brady, the Patriots remain a team stocked with veterans in a mediocre division with one of the most successful coaches in NFL history.
"The leadership on this team will take care of itself," offensive lineman Matt Light said. "I expect [Cassel] to do his job, and that's the same thing he expects from each one of us. There's nobody on this team that we don't have confidence in. You can't have a better mentor than Tom Brady."
The Patriots have just two quarterbacks on the roster: Cassel and rookie Kevin O'Connell. Matt Gutierrez, who signed as an undrafted free agent before the 2007 season and has thrown one career pass, was released in the final cut-downs before the season.
Belichick, who runs one of the most secretive operations in the league, initially denied the team reached out to any other quarterbacks, but sources told Mortensen on Monday that Simms and Rattay were indeed in Foxborough.
They were scheduled to work out, but when they arrived at the Patriots' facility, vice president of player personnel Scott Pioli told them that "circumstances have changed" and sent them back to the airport.
So for now, Cassel is Belichick's quarterback.
"I'm happy for his opportunity to have a chance to play," said Leinart, who, ironically, is now a backup with the Arizona Cardinals. "I'm bummed for Tom. You just hope he can heal as well as he can and get back out there as soon as he can. But Matt will step up. I think he'll be all right."
Pollard, who apologized to Brady immediately after the play, said Monday that it was an accident and prayed for Brady's speedy recovery.
"I can't change what happened," he said. "As soon as the play happened, I said, 'Oh, man.' When I heard him scream, I knew it was serious."
Pollard, a third-year safety known as one of the most considerate and cooperative players on the team, said he received messages of support from friends and fans all over the country.
"I know one of their teammates called me a dirty player. If you see the play, I was not being dirty at all," Pollard said. "I was trying to get up and my momentum took me forward with 230 pounds on my back. I've never been a dirty player. You ask my teammates. You ask any of my coaches."
While not calling Pollard's play dirty, Belichick said his players are taught to hit quarterbacks between the knees and shoulders. Patriots defensive lineman Vince Wilfork complained that he was penalized and fined for a hit similar to Pollard's, but league spokesman Greg Aiello said supervisor of officials Mike Pereira determined it was legal.
"It is not a foul because the defensive player was coming off and affected by a block by the offense," Aiello said.
A former fourth-stringer who was the 199th overall selection in the 2000 draft, Brady himself took over at quarterback when longtime starter Drew Bledsoe sustained a life-threatening chest injury in a 2001 game against the New York Jets. Brady led the Patriots to their first NFL title that season, another in 2003 and another in 2004.
But he missed the entire preseason with an unspecified foot injury, then left the season opener 7:33 into the first quarter.
After being tended to on the field, Brady walked off, limping, between two trainers. He went to the locker room and wasn't seen on the sideline again.
"We feel badly for Tom about the injury," Belichick said Monday. "You hate to see anyone go down. No one has worked harder or done more for this team than Tom has."
Information from The Associated Press was used in this report.