Game of role reversal stings these champs

FOXBOROUGH -- This was the antithesis of everything they've done.

The New England Patriots have come to personify preparation, discipline, and, above all, the uncanny ability to successfully implement the right play at the right moment.

Where were those instincts yesterday? They were embedded along the sideline of the San Diego Chargers. Quarterback Drew Brees was Tom Brady, a poised, patient leader who delivered on every big throw. Running back LaDainian Tomlinson was Corey Dillon, circa 2004, a prolific back with the added upside of corralling catches at crucial times. Coach Marty Schottenheimer was Bill Belichick, a master play-caller who diagrammed one successful offensive set after another, while instructing his defense to bend but not break in the second half.

The Chargers' defense relinquished 0 points to Brady and the boys in those final two quarters.

That's right. Zero.

Conversely, New England's depleted defense coughed up 41 points -- including 24 unanswered ones. They allowed their visitors to convert on six of their eight third-down chances in the second half, and looked decidedly dispirited in the process.

Such numbers are normally blasphemy here in the land of the lighthouse. The Patriots' success long has been tied to the big play from the defense when the game was on the line, whether it was a jarring Rodney Harrison hit to cough up the ball, or a Tedy Bruschi leap-in-from-nowhere interception, or a Richard Seymour not-in-my-house sack.

Two of those three are gone for the year. The one left standing stood by his locker yesterday and tried to make sense of his team's first defeat at home since Dec. 22, 2002, a string of 21 consecutive victories. The loss of Harrison, who shredded his knee against Pittsburgh last week, reverberated in this game, particularly when Tomlinson ran free, as did the less-discussed but equally important void left by offensive lineman Matt Light (broken leg).

''There's no replacing a guy like [Harrison], but that's no excuse for what happened today," Seymour said. ''We should be able to stop the run. That starts with myself, and the other guys up front. If we do our job, it shouldn't matter who is in the secondary.

''The defensive line didn't get it done. Put this loss on us."

It isn't quite that simple. New England knows its secondary, which has some of its best players in street clothes (Harrison, Randall Gay, Tyrone Poole) is vulnerable. Even so, it's rare to see receivers get behind the Patriots defenders, as they did yesterday. You don't often see New England give up multiple long balls for big gains, but Duane Starks and Guss Scott were victimized accordingly. Veteran Eugene Wilson was tagged with a costly 44-yard interference call, and Chargers tight end Antonio Gates (6 grabs, 108 yards) all but filed the paperwork for his Hall of Fame induction with his performance yesterday.

Then there's Tomlinson, who, pound for pound, thus far has earned the right to tout himself as the best running back in the NFL this season. He destroyed the Patriots by running for 134 yards and two touchdowns with a combination of elusiveness and power, then chipping in with three catches for 34 yards. In all, his team churned out 431 total yards of offense.

''For the most part," offered Wilson, ''they were one step ahead of us. I wouldn't say there were too many things that turned out right for us."

Losing is one thing. Being manhandled is quite another. New England folded in the second half, and that's not an encouraging development. The only lingering question is how in the name of Dan Fouts did these Chargers start the season 1-2?

''They did a better job of everything," offered a subdued Belichick. ''They got anything they wanted."

Now come the tough questions. Can the Patriots secondary regroup, or is this a glaring weakness that will remain while they wait for Gay and Poole to find their way back on the field? Then there's the matter of Dillon, who rushed for 63 yards yesterday. Obviously when your team falls behind, you take to the air, but Dillon's numbers after four games (73 rushes, 223 yards, a 3.1 yard average) are pedestrian. Is it the offensive line, which is trying to make do with two rookies, the back (who broke one for 29 yards yesterday), or both?

New England's players know better than to point fingers -- unless it's at themselves. They knew they were in trouble when their diehard fans began streaming for the exits (to watch the Red Sox clinch the wild card, no doubt) with more than five minutes to play. For the first time in recent memory, the traffic was flowing freely on Route 1 just one hour after game time.

Few cared to stick around to see the maudlin finish, which included linebacker Mike Vrabel picking up an uncharacteristic facemask penalty against Tomlinson, and Brady throwing an uncharacteristic interception. The frustration was palpable. The defending champions haven't given up this many points since they lost to the Atlanta Falcons, 41-10, Nov. 8, 1998. That's almost seven years ago. In other words, it's the worst defensive effort since Belichick came aboard.

The ever gracious Schottenheimer tried to put the game in perspective.

''You look at the Patriots and every time they are faced with adversity that injuries bring to [their] team, they have managed to step up," he said. ''It had to be difficult for them today. I counted eight new starters they didn't have a year ago, and I think that's a problem for anybody."

That problem won't be solved anytime soon. The Patriots are going to be shorthanded the rest of the way. The beating they absorbed yesterday is the kind they've been dishing out for the better part of four years.

So now we'll find out what these Patriots are truly made of. If they can rebound after a loss like this, they will be fine. If they can't, it will be a long season.

''We just played bad," said receiver Deion Branch (one catch, 6 yards). ''We'll look at all the terrible things we did on film and correct it."

The Patriots have said that before after a home game. But usually they've played badly and won. Those days are over, and the margin of error is shrinking. Suddenly, nothing is a given.

If Rodney Harrison was still in the mix, he'd turn such doubts into all sorts of passionate fodder for his spirited defense.

But Harrison is gone, and he isn't coming back -- at least not this season.

Let's see who is ready to step up in his place.

Jackie MacMullan is a Globe columnist. Her e-mail address is macmullan@globe.com.