FOXBORO — How many times have we seen this?

How many times have we seen the Patriots’ defense fold in the final minutes? How many times have we seen it collapse in crunch time? How many times, in big games, have we seen the defense blow a game the offense seemingly had won?

There was last year’s Super Bowl, when the Giants drove 83 yards in the final 2:42 for the game-winning touchdown that spoiled New England’s perfect season.

There was the AFC Championship Game the year before, in Indianapolis, when the Colts covered 80 yards in a come-from-behind 38-34 victory.

And there was last night, at Gillette Stadium, with first place in the AFC East at stake, when, after Matt Cassel had led not just one, but two, Tom Brady-like comebacks, the defense collapsed — not just once, but twice.

Cassel was nothing short of fabulous. The New England defense, unfortunately, came up short yet again, able to do nothing to stop Brett Favre and the N.Y. Jets when it counted most.

How many times have we seen this?

Too many times.

Which is ironic, because defense is supposed to be Bill Belichick’s specialty.

Defense also is supposed to win championships. Which is why the Patriots didn’t win the Super Bowl last year, didn’t get to the Super Bowl the year before, and may not even get to the playoffs this season.

The playoffs seemed very much in doubt when Brady was lost for the season in the first quarter of the first game. After all, Cassel, his backup, hadn’t started a game since high school.

But he’ll certainly be starting somewhere next year, having proved himself a playoff-caliber quarterback last night, when he earned the respect of the Jets and a national television audience, and also earned himself a free-agent deal the Patriots won’t be able to match when the four-year deal he signed as a seventh-round draft choice in 2005 expires after this season.

Who wouldn’t want Cassel after the performance he put on last night?

The Patriots were trailing, 24-6, late in the second quarter, but he threw a touchdown pass 15 seconds before halftime and then threw another — followed by a two-point conversion toss — on the final play of the third quarter, cutting the Jets’ lead to 24-21.

New England tied the score at 24-24 with 10:22 to play, and there seemed little doubt, at that point, that, if the defense could only get the ball back for Cassel, he’d put more points on the board.

Unfortunately, they couldn’t.

With anyone other than future Hall of Famer Brett Favre at quarterback, the Jets might have been rattled after seeing their commanding lead disappear. But, unruffled, Favre directed a 14-play, 67-yard touchdown drive that consumed 7:06 and put New York back on top, 31-24.

That was the score when New England got the ball for what clearly would be the last time — at its own 38, with no timeouts, and only 1:04 remaining.

Amazingly, dazzingly, Cassel led the Patriots to a touchdown.

He completed 5 of 8 passes — really 5 of 5, because his only incompletions were spikes that stopped the clock — the last of which was rifled to a diving Randy Moss near the right edge of the end zone from 16 yards away on fourth down, with one second remaining.

That sent the game into overtime.

Which meant the coin toss was likely to determine the outcome.

At that point, Cassel seemed unstoppable. He was red-hot, on a roll, completing 30 of 51 attempts for 400 yards — all career-highs — and three TDs, equaling his total in a romp over the Broncos.

The problem was that it seemed highly unlikely the New England defense could stop Favre and the Jets.

As proved to be the case.

“It’s very frustrating,” said Cassel, in what rates as the understatement of this Patriots season. “You want to be out there. You want to have the ball in your hands. You want to have an opportunity to win the game.”

Unfortunately, he never had that chance, as, yet again, the defense failed to come through in the clutch.

Cassel was trying to look on the bright side afterward.

“Anytime you come back from 24-6 deficit,” he said, “that’s something you should be proud of — to show that type of fight and tenacity.

“I hope,” he added, “I’ve earned the confidence of these guys.”

He’s earned that, and likely a rich, new contract somewhere else next season.

Where, hopefully, he’ll have a defense that can get him the ball.

jdonalds@projo.com