FOXBOROUGH, Mass. — Three times the Chargers crossed the 10-yard line. And three times the Patriots stopped them from crossing the goal line.

Against a record-breaking offense like New England's, three field goals instead of three touchdowns are simply not enough.

So the Patriots are headed to the Super Bowl — a 19-0 season just a single win away — after yesterday's 21-12 win over San Diego behind a red-zone defense that wouldn't budge after being battered most of the season.

"Defense wins championships," cornerback Ellis Hobbs said. "Tonight you saw that, how time and time again those guys got in the red zone and time and time again we kept saying, 'no, no, no, no, not today' — making them score field goals and eventually the offense started clicking."

Flash back to eight days earlier and gauge the improvement: Jacksonville scored two touchdowns when it got inside the New England 10, but still lost 31-20 in the divisional playoff game.

And two weeks before that? The Giants scored touchdowns all four times they crossed the Patriots' 20 — all on Eli Manning's passes — in New England's 38-35 win in the final regular-season game.

This time, the Patriots intercepted two of Philip Rivers' passes, one leading to a touchdown, and erased any doubts their linebackers were too old or their defensive backs too slow.

They are, simply, too good.

"The Chargers are a very productive team in the red zone and, obviously, we were struggling. We stepped up big," safety Rodney Harrison said. "We have a lot of room for improvement, but, for once, I'm going to sit back and I'm going to enjoy this one."

In their first 13 games, the Patriots allowed touchdowns on 20 of 28 series in which opponents reached the red zone.

During the second half of the season, however, they showed they could win close games after beating their first eight opponents by at least 17 points each.

"Even in all our championship years that never happened on a consistent basis," said linebacker Tedy Bruschi, part of three Super Bowl winning teams in the past six seasons. "These are the games we're used to. This is what we consider Patriots football."

Their first big defensive stop came late in the first quarter when San Diego had a first-and-goal at the Patriots 9. Michael Turner ran for just 1 yard, Rivers followed with two incompletions and Nate Kaeding kicked a 26-yard field goal to make it 3-0.

Trailing 7-3 in the second quarter, the Chargers moved from their 30 to another first-and-goal at the 9.

Turner rushed for 1 yard. Rivers then threw toward Antonio Gates, but linebacker Bruschi dived in front of him at the last second to slap the ball away near the goal line. Rivers then hit Chris Chambers in the left flat, but Hobbs made an open-field tackle at the 5.

"I'm the last line of defense," Hobbs said. "I knew if he got past me that was it. He had cut back out on Rodney and my thing was just get him down anyway you can, just shoot at his legs, can't run without those."

The Chargers settled for another field goal, this one for just 23 yards that cut the lead to 7-6.

With the Patriots ahead 14-9, Rivers led the Chargers downfield again.

With a third-and-2 at the New England 4, Turner took the handoff and started up the middle. Linebacker Junior Seau penetrated, forcing Turner to veer left, and Seau tackled him for a 2-yard loss.

No first down. No chance for a touchdown.

"The defensive linemen did a great job of taking up two guys," said Seau, who shot through the gap. "It was a great call."

Not for Turner.

"He read the play," Turner said. "I saw him starting to run to the spot. I had to beat him there, but he got a great jump. It was designed to go up the middle."

Kaeding came out again and kicked a 24-yard field goal, another wasted opportunity and a 14-12 lead for New England.

It was 21-12 when San Diego started moving again, from its 16 to a third-and-10 at the New England 36.

This time, the aggressive Harrison ran in from Rivers' right side, hit the quarterback as he was throwing and forced an incompletion.

"I was able to just come free," Harrison said. "I think he felt my pressure and he got rid of the ball, and every time you get a shot on the quarterback, you want to try to knock their lights out."

With 9:21 left, San Diego was forced to punt and Kaeding never saw the field again.

Not even after he scored all his team's points as the Patriots defense denied the Chargers time after time inside the 10.

"I just said 'we got to hold 'em to three points, fellas,' " Harrison said. "If you can keep them in the red zone to three points, that's a victory."