BOSTON (AP) — The NBA’s most-decorated team avoided the biggest playoff collapse in league history and earned a chance to hang an unprecedented 18th championship banner from the rafters.

Paul Pierce had 31 points and 13 rebounds, and little-used backup Nate Robinson gave the Celtics a boost with 13 second-quarter points as Boston beat the Orlando Magic 96-84 on Friday night, earning a chance to play for a second NBA title in three years.

The finals will begin Thursday in either Los Angeles or Phoenix.

The Lakers lead the Western Conference finals 3-2, and a victory over the Suns in Game 6 on Saturday would set up the cross-coast rivals for a rematch of the 2008 finals — and 10 other championship series from 1959-87.

“We got back to moving the ball, playing good defense, not allowing them to shoot the 3-point shot. That was the key,” Pierce said.

The Boston fans have been chanting “Beat L.A.!” since Game 3, when the Celtics cruised to a 3-0 lead in the best-of-seven Eastern Conference finals. Orlando won the next two games and threatened to become the first team ever in the NBA — but the second in Boston this month — to come back from a 3-0 deficit in a playoff series.

The Bruins opened a 3-0 lead against Philadelphia in the NHL’s Eastern Conference semifinals before the Flyers rallied to win — in the very same building.

The Magic, who dressed in the same locker room where the Flyers celebrated their comeback, couldn’t match it — or even force the series back to Orlando for a Game 7.

“The starting five has never lost,” Boston coach Doc Rivers said. “This starting five has never lost a series, ever. We believed that coming into the season, and we just kept believing.”

Dwight Howard had 28 points and 12 rebounds as the defending East champions failed to get back to the finals. Vince Carter scored 17 points, and Jameer Nelson finished with 11 points and four assists as he was outplayed by Boston’s starting point guard, Rajon Rondo, and Robinson, his backup.

Reporters and fans snickered when Rivers said last month that Robinson, who had struggled to get playing time and contributed little since coming to Boston at the trade deadline and had never appeared in the postseason before, “He’s going to win us a playoff game.”

But Robinson came off the bench at the start of the second quarter, when Boston led 30-19, and hit 3-pointers 90 seconds apart to help stretch the lead to 15 points. Boston led 44-25 when Robinson stole a bad pass from Carter and took off on the fast break, getting bowled over at the other end to draw a flagrant foul on Nelson.

The free throws gave Boston a 21-point lead — its biggest of the first half.

“You know, he really won this game for us because the game was in the mix to go either direction and he really gave us a spark,” Pierce said of Robinson. “… That’s really growing up, really growing into a man tonight.”

Orlando cut it to 13 points at halftime, but the Celtics scored 11 of the first 13 points in the third quarter and never led by fewer than 14 in the fourth until the final minute.

By that point, the Celtics were already dancing on the sidelines, wearing the Eastern Conference championship hats and T-shirts that had been standing by since Saturday, when they cruised to a 94-71 victory to take a 3-0 lead in the series. When it was over, Hall of Famer Dave Cowens presented owner Wyc Grousbeck with the conference trophy and told the team, “Bring home No. 18, now.”

Ray Allen scored 20 points for Boston and Rondo had 14 points and six assists. Glen “Big Baby” Davis returned to the court just two days after a scary concussion left him staggering around the court in Game 5 and scored six points with seven rebounds in 18 minutes. He entered the game to a standing ovation and left to another.

“I thought early on we were OK, we just didn’t make shots, and then we let it get to us and when we did it broke down,” Magic coach Stan Van Gundy said. “And I thought two things happened to us also, Nate Robinson was huge in the first half, that was a huge, huge lift for them, to have 12 points in the first half, and I also thought the other key part of the game … Ray hit the two 3s, bang, bang in the second half.”

NOTES: Rondo hit the court hard and was slow to get up after he was fouled by Jason Williams late in the final minute of the first quarter. He stayed in the game and hit both free throws. … The Celtics are 9-2 against the Los Angeles and Minneapolis Lakers in the finals. The Celtics and Suns have met once in the finals, when Boston won 4-2 in 1976. … Celtics F Rasheed Wallace left the game in the fourth quarter with back spasms and did not return. He had no points — shooting 0 for 5 — and three rebounds in 12 minutes.