FOXBORO, Mass. -- It could turn out to be a seven-and-a-half minute season for the Patriots, over almost before it started.

Or, looked at another way, it could turn out to be a very long season, one that makes Napoleon's retreat from Moscow seem like a stroll in the park.

Until we know how badly Tom Brady is hurt, we just don't know.

Brady has never missed a start since taking over for Drew Bledsoe in the second game of the 2001 season, putting together a string of 127 in a row, including playoffs.

Playoffs? As former colts Colts coach Jim Mora once shrilly said. Playoffs?

With Brady at quarterback, the Patriots are a Super Bowl contender. Even a Super Bowl favorite. Without him, as we saw yesterday, they're lucky to beat the Kansas City Chiefs, losers of their last nine games last year, when they finished 4-12, tied for last in the AFC West.

If the Patriots are very, very lucky, Brady will be in the lineup Sunday against the Jets at the Meadowlands.

But if you saw him hobble off the field midway through the first quarter Sunday afternoon, his left knee dragging, pain and anguish clearly showing on his handsome face, you know the odds on that are greater than filling an inside straight on the final card.

It didn't look good. Not good at all. And, if it isn't, then the Patriots' postseason chances aren't looking so hot, either.

He's the one guy they can't lose. Not if they want to win the Super Bowl. Or the AFC championship. Or even the AFC East.

Brady's won three Super Bowls, and would have won four if the New England defense had been able to keep the Giants from driving 83 yards to a touchdown in the final 2:42 in February in Phoenix. He's a two-time Super Bowl MVP. He threw an NFL record 50 touchdown passes last season as the Patriots rolled undefeated all the way to Super Bowl XLII.

His backup, Matt Cassel, hasn't started a game since high school.

That's right -- high school.

Cassel went to Southern Cal out of Chatsworth, Cal., High, and wound up playing behind a couple of Heisman Trophy winners: Carson Palmer and Matt Leinart. Drafted in the seventh round by New England in 2005, he managed to make the team and has since made his living as Brady's seldom-used backup.

That role was in doubt as recently as 10 days ago, when some sportswriters were speculating that, with the Pats having four quarterbacks on the roster, and likely to keep only three, Cassel would be the odd man out -- losing out to Matt Gutierrez, who had better numbers in the preseason, and third-round draft choice Kevin O'Connell.

But coach Bill Belichick decided to stick with him, and that decision paid dividends yesterday, when Cassel came off the bench and, with the Pats facing third and 11 at their own 1-yard line, lofted a 51-yard completion to Randy Moss. Eight plays later, Cassel threw to Moss again for 10 yards and a touchdown, giving the Patriots a 7-0 lead.

"That first throw," Wes Welker said, "was huge."

What's much bigger is Brady's importance to the Pats.

Although the sun was shining brightly yesterday, a very dark cloud suddenly hovered over this Patriots' season when blitzing safety Bernard Pollard, trying to get past blocking back Sammy Morris, clawed his way to Brady's feet and rolled up on him as he brought him down.

It was frighteningly similar to the tackle made on Palmer in the 2005 playoffs by Kimo von Oelhoffen of Pittsburgh.

"The one on Carson," recalled veteran cornerback Deltha O'Neal, who was picked up by the Pats only last Monday, after being cut by the Bengals, "looked like [von Oelhoffen] was trying to do that. Other people say it was an accident. All I know is, you go til the whistle blows. They need to put a rule in that you can't go for the quarterback's legs."

Actually, there is such a rule. Known as the "Kimo rule," it is, in actuality, Rule 12, Section 2, Article 12-5, which states: A rushing defender is prohibited from forcibly hitting in the knee area or below a passer who has one or both feet on the ground, even if the initial contact is above the knee. It is not a foul if the defender is blocked (or fouled) into the passer and has no opportunity to avoid him."

An optimist would say that Cassel may have an opportunity similar to that of Brady, who was a virtual unknown when he replaced Bledsoe, having been drafted in the sixth round out of Michigan only the year before.

"Since I've been here, and been around Tom, he's always popped back up," Cassel said. "But this is something I've been preparing for a long time, although it's not something that we expected to come up on opening day."

You know it can happen on any play. That it hasn't happened before to Brady has been his -- and the Patriots' -- good fortune.

Now, their fortunes are very much up in the air, like a long pass in the closing seconds with the game on the line.

Now, it's the Patriots' season that's on the line. There'll be lots of gnawed nails and restless nights in New England until Pats fans find out when -- or if -- Brady will be back.