The Celtics’ Kevin Garnett, knowing the importance of winning Game Five, gets himself and the crowd at the TD Banknorth Garden revved up in first-play action last night.

The Providence Journal / Glenn Osmundson

BOSTON – The Celtics are one victory from their first NBA Finals since 1987, but they could just as easily be one game from elimination.

Leading by 17 points three times in the third quarter, they barely withstood a furious Detroit fourth-quarter rally and escaped with a 106-102 victory last night for a 3-2 lead in the Eastern Conference Final.

Boston can advance with a victory tomorrow night at the Palace at Auburn Hills or, if Detroit wins and forces Game Seven, Sunday night here at the TD Banknorth Garden.

Kevin Garnett led the Celtics with 33 points, but Ray Allen, mired in a shooting slump for most of these playoffs, sparked them with a brilliant 29-point effort, his playoff best this year. Kendrick Perkins turned in a superb 18-point, 16-rebound, 2-blocked shot effort, and Paul Pierce scored 16 points. Point guard Rajon Rondo struggled with his shot (3-for-14 for 7 points) but passed for 13 assists, made four steals and blocked a shot.

James Posey’s three-pointer was the only point production from the bench.

"Everyone brought their A game tonight, and that’s why we won. We don’t get those efforts, we don’t walk out with a win tonight," Pierce said. "This was a huge game. If we don’t get this game, we put ourselves in position of having to win in Detroit."

The Celtics did win Game Three there last Saturday, their only road triumph of the playoff season. They did not want to return to Motown needing a victory and would prefer to end this series tomorrow night to avoid a third Game Seven this postseason.

"We’ve just got to think about the next game. We’ve got to have a great focus and a great intensity there. You know, they’ve won titles. They’ve been in this position before. We just have to go in there and play our game. That’s the whole key," coach Doc Rivers said.

Detroit seemed out of it after a pair of Perkins free throws gave Boston an 84-67 lead with 1:19 remaining in the third quarter, but Detroit started the fourth quarter with a 14-5 run and cut Boston’s lead to six points. With Chauncey Billups scoring 9 of his team-high 26 points and Richard Hamilton 9 of his 25 in the fourth, the Pistons continued to charge, twice slicing the lead to a single point, 100-99 with 1:23 remaining and 102-101 with 8.2 seconds to play.

In both cases Allen restored a three-point lead, the first with a 21-foot jump shot and the second with a pair of free throws. Garnett’s free throws with 3.4 ticks on the clock after Rodney Stuckey had made one of two freebies provided the final margin. Detroit outscored Boston, 31-22, in the final 12 minutes.

"It was the longest fourth quarter out of all the games we played in. I was a little disappointed in the way we played in the fourth quarter," Pierce said. "We’ve got to be a little bit more aggressive in the fourth than we were. I thought we just kind of let the time pass away and hoping we were going to win the game."

The Celtics survived the fourth-quarter meltdown because they roared out of their dressing room for the start of the third quarter and blitzed the Pistons with a 10-3 run for a 62-49 lead. Then Allen, the Rip Van Winkle of these playoffs, awoke. He buried back-to-back three-pointers for a 68-54 lead, passed to Garnett for a jump shot on the left, made a free throw, made a lay-up after an offensive rebound for a 17-point advantage (75-58), drove in from the right for a lay-up and then raced along the baseline, caught a pass and buried a trey from the right corner.

He scored 16 of Boston’s 32 third-quarter points and had 24 going into the fourth.

"Just his presence on the floor alone is a great help. Tonight he just happened to have it really, really going, and we’re going to need that from him. If he plays like that, it’s tough to beat us,"

Pierce said.

Allen took his 9-15 shooting – 5-6 from three-point range – in stride.

"My feeling now is no different from if I had scored 10 points and we still won the game. . . . Winning gives me the greatest joy regardless of what I’ve done . . . " he said.

Garnett mentioned the third quarter as a key to the game for Boston.

"I thought the third quarter was big for us. We came out with a lot of energy," he said. "They made a run . . . but for the most part you know they’re going to make a run. You know they’re experienced, and they’ve been in a lot of pressure situations."

Detroit put Boston in a pressure situation by refusing to quit in the fourth quarter.

"We fought back and made it a game, and it could have gone either way at the end," Billups said.

"I told our guys after the game I was proud of them," Detroit coach Flip Saunders said. "We’re not going away. They had guys that played a heck of a game. They got three points off their bench. We struggled at times rebounding-wise (42-25, Boston), and we still had opportunities down the stretch.

"We didn’t rebound, but we did a lot of other good things to put ourselves I position to be in the game. That was the surprising thing, that we were in the game at the end. I’m sure everybody was surprised," he added.

Shocked is more like it. And, for the Celtics and their fans at the very end, relieved.

mszostak@projo.com