Boston ? When the final buzzer sounded and the miracle was complete, the Boston Celtics celebrated like it was the end of Game 7 instead of Game 3.

Paul Pierce’s teammates mobbed him at center court until he broke free and jumped atop the scorer’s table.

Coach Jim O’Brien’s ever-present poker face disappeared, the most stoic of NBA coaches pumping his fist to the crowd and walking triumphantly off the court.

The Celtics pulled off the greatest fourth-quarter comeback in NBA playoff history Saturday night, with former Kansas guard Pierce scoring 19 of his 28 points in the final 12 minutes as Boston overcame a 21-point deficit to beat the New Jersey Nets 94-90.

“It was purgatory, it might have been closer to hell for three quarters, but that last one was Eden. Damn, that was great,” O’Brien said.

No team had ever come back from more than an 18-point deficit at the start of the fourth quarter, and Pierce certainly didn’t look like a candidate to rescue his team after missing 12 of his first 14 shots.

But he began driving the ball to the basket with reckless abandon in the final quarter, and the Celtics never relented as they outscored the Nets 41-16 in the fourth to take a 2-1 lead in the best-of-seven Eastern Conference finals.

“At the start of the fourth quarter we just wanted to fight and make a statement for the next game that we’re going to be a team to be reckoned with. I think we did more than make a statement,” Pierce said.

“If I was on the other end of this, I would be hurting right now.

“I think this is a chance for us to gain momentum and take control of the series and not look back.”

The previous largest comeback from a deficit after three quarters was when the Phoenix Suns, after trailing 100-82, beat Houston 124-117 in overtime on May 11, 1994.

This one seemed lost at the end of three, and Pierce noted that the Nets’ reserves were laughing at the Celtics.

Antoine Walker spoke up in the huddle, telling Pierce and his other teammates that they had to do something to regain some respect.

None of them could have imagined what was in store.

“I’ve never been a part of anything like this in my life,” said Walker, who added 23 points and helped keep the Celtics within striking range if being down by as many as 26 can rightfully be called striking range until the fourth.

The charge began the moment the Celtics touched the ball to begin the period as Pierce scored three baskets from inside during an 11-0 run that got the crowd back into the game and cut the Nets’ lead to 74-64.

The teams traded baskets for the next five minutes, with the Celtics never trailing by more than 13 or less than eight until Rodney Rogers hit two free throws with 3:12 left to make it 88-82.

The crowd, which had been kept silent for the first three quarters, kept getting louder and louder as Boston crept closer.

“I couldn’t even hear myself in that fourth quarter, and I think they were kind of intimidated by the crowd and the simple fact that we were gaining momentum,” Pierce said. “They didn’t have anybody out there who was going to be aggressive and step up for them.”

Pierce got inside for his sixth layup of the quarter to make it 90-87 with 1:37 left, then hit a pair from the line to pull Boston within a point with 1:07 remaining.

After Kerry Kittles missed a 3-pointer, Pierce was fouled going to the basket with 46 seconds left. He made both shots, giving the Celtics their first lead since 1-0.

Kittles lost his dribble on the ensuing possession, and Kenny Anderson scooped up the loose ball and went in for a layup that was goaltended by Kittles.

New Jersey’s Keith Van Horn got caught off his feet and flung up a wild shot that missed horribly with 22 seconds left, and Pierce made one of two from the line moments later for a four-point lead.

Jason Kidd missed four 3-point attempts the rest of the way as the Nets completed their collapse.

“It hurts, but the series isn’t over,” Kidd said. “We let a golden opportunity slip away.”

Pierce scored the most fourth-quarter points in the NBA this season, with an astonishing 57 of his 552 points in the period coming in Boston’s four regular-season games against New Jersey. Pierce began the fourth quarter having missed 39 of his 53 attempts.

Anderson added 15 points in his best game of the series, and Rogers added 10 six of them coming on foul shots in the fourth as Boston kept chipping away.

Kidd had 19 points for the Nets, whose only go-to player in the final 12 minutes was backup center Aaron Williams.

New Jersey shot 4-for-22 with six turnovers in the final 12 minutes, while Boston was 11-for-19 from the field and 18-for-21 from the line.

The Nets after letting an early 16-point lead drop to six opened a 20-point halftime lead. A jumper by Van Horn gave New Jersey its largest lead 65-39 with 8:31 left in the third.

The score was 74-53 at the end of three quarters, and the Nets’ lead seemed safe. But Pierce and the Celtics didn’t quit, and now they will take a boatload of momentum into Game 4 on Monday night.

“I don’t think our guys will be that dejected. … I think they understand that this is a game that we blew,” Nets coach Byron Scott said. “We had the game and we blew it. And our guys, they’ve been very resilient all season, so I’m sure we’ll come back with the same type of effort we had in the first three quarters “

Notes: The Celtics stretched their home winning streak to 11 straight, including 6-0 in the postseason. … Van Horn picked up two fouls in the first 39 seconds of the game. His replacement, Richard Jefferson, had six points, five rebounds and four assists over the remaining 11:21 of the first quarter.

Celtics 94, Nets 90

NEW JERSEY (90)

Martin 5-12 1-2 12, Van Horn 3-6 0-0 6, MacCulloch 2-3 1-2 5, Kidd 6-16 0-1 12, Kittles 8-20 3-4 19, Jefferson 4-10 0-2 8, A.Williams 6-8 6-7 18, Harris 4-9 0-0 10, Collins 0-0 0-0 0, Johnson 0-2 0-0 0. Totals 38-86 11-18 90.

BOSTON (94)

Walker 8-18 5-6 23, E.Williams 1-5 3-4 5, Battie 2-8 2-2 6, Anderson 6-13 3-4 15, Pierce 8-21 12-15 28, McCarty 0-2 0-0 0, Rogers 2-4 6-6 10, Delk 2-7 2-2 7. Totals 29-78 33-39 94.

New Jersey 28 26 20 16 90

Boston 13 21 19 41 94

3-Point GoalsNew Jersey 3-20 (Harris 2-3, Martin 1-1, Van Horn 0-1, Johnson 0-1, Kittles 0-7, Kidd 0-7), Boston 3-16 (Walker 2-3, Delk 1-3, McCarty 0-2, E.Williams 0-3, Pierce 0-5). Fouled outMartin, A.Williams. ReboundsNew Jersey 57 (MacCulloch 11), Boston 53 (Walker 12). AssistsNew Jersey 26 (Kidd 11), Boston 15 (Walker, Pierce 4). Total foulsNew Jersey 34, Boston 21. TechnicalsKidd, Pierce, Rogers. A18,624 (18,624).