The coach or the quarterback? The quarterback or the coach?

Maybe now we'll finally get our answer.

In what was truly a worst-case scenario, the Patriots lost quarterback Tom Brady to a knee injury at Foxborough today on their 16th offensive play ... of the season. Brady limped off the field and never came back. Lifelong backup Matt Cassel came off the bench to lead the Pats to a 17-10, season-opening victory over the rebuilding Kansas City Chiefs, but it certainly felt like the entire 2008 campaign crumpled to the ground in a heap.

Prepare for the worst, Pats followers (Update: Belichick confirmed your worst fears Monday -- Brady out for the season). This was one of those times when it seemed no MRI was necessary to give you a diagnosis.

The pit in your stomach was enough.

"Any time you have a starter go down, no matter if it is your quarterback or anybody [else], I think it hurts,'' Pats receiver Randy Moss told reporters after the game. "By [Brady] being the face of the New England Patriots and Tom being who he is -- and the competitor that he is -- it actually ... it kind of hurts to be honest with you. I know the show must go on and hopefully Matt Cassel is ready to step in. From a team standpoint, we are ready to embrace him and let him lead us.

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"I don't know what Tom's situation is; I don't know how serious it is. ... I was talking to Jabar Gaffney toward the end of the game after [Brady] went in the locker room, [and] every time the fans cheered I looked over at the door [of the locker room tunnel]. I was like a little kid at the candy store just hoping you would see that No. 12 come out those doors and up the steps. Like I said, every time the fans cheered I looked at that door, so basically I was just snapping my neck around every time.''

Don't hold your breath.

Brady might not be walking through that door anytime soon.

So now, the obvious question: Where do the Patriots go from here? Late Sunday afternoon, Patriots players spoke about picking up the slack in the absence of their leader, but this really is not about them anymore. Rather, it is about their coach, the estimable Bill Belichick. More than Bill Parcells and Drew Bledsoe, more than the entire Kraft family, the tandem of Belichick and Brady has made the Patriots what they are today. Since the early stages of the 2001 season, when Mo Lewis knocked Bledsoe senseless, the Patriots have always had the security and comfort of a B&B, granting all of New England a certain coziness in even the most difficult and hostile circumstances.

The Patriots didn't merely have the best coach.

They had the best quarterback, too.

Along the way, while the Patriots were going to five AFC Championship games and four Super Bowls while winning three league titles, we encountered a chicken-and-egg conundrum: Who comes first, the quarterback or the coach? Seemingly, the Patriots have won because they had Belichick first and Brady second, Belichick second and Brady first. In the end, all that really mattered was that the Patriots had them both, simultaneously, which gave them two unflappable and impenetrable decision-makers in a game in which decisions must be made quickly and decisively.

Consider this: With Brady as his starting quarterback, Belichick is 87-24 as a head coach during the regular season, 14-3 during the postseason. He is 3-1 in Super Bowls. Without Brady, Belichick's career regular season record is a mere 41-57 and he is 1-1 in postseason play. (Gulp.)

As such, now might be a good time to point out that the Patriots will likely be forced to change their entire offensive approach without Brady. Over the last seven or eight years, New England's entire attack has been built on Brady's ability to read defenses, make the right choice, find the open man. His mind and his poise always were his best weapons. From David Givens to Deion Branch to Doug Gabriel and Randy Moss, the Patriots always have said that the receiver they throw to is the one that's open. Unsaid in all of that was that they had a quarterback who could find the open man, almost unfailingly, and who played the rest of the NFL like a pinball machine last year when the Pats finally got him some big-time receivers.

Now, Brady appears to be headed to the sideline for an extended period of time, which would offer Belichick arguably the greatest challenge of his coaching career: Can he win without Brady? The Patriots have great depth at running back, a stable of first-round draft picks on the defensive line, three Pro Bowl linemen protecting the quarterback. They have some accomplished veteran linebackers and a bright, promising young one. They have some question marks in the secondary and arguably the best tandem of starting wide receivers in the NFL.

What the Patriots might have, too, is an enormous void at quarterback that could unmask or further elevate one of the great coaches in NFL history.

So what do you think:

Does Bill Belichick need Tom Brady more than Tom Brady needs Bill Belichick?

Share your thoughts in the comments section.