BOSTON -- Twelve years without advancing in the playoffs. Two failed attempts to close out the Boston Celtics. Nineteen consecutive missed 3-pointers.
Carmelo Anthony brought all the slumps to a stop.
Anthony made a pullup jumper and then sank his first 3-pointer in 20 tries to help the New York Knicks turn back Boston's comeback attempt on Friday night, beating the Celtics 88-80 in Game 6 to win a playoff series for the first time since 2000.
"You should never play with any doubt out there on the basketball court," Anthony said. "I can't step onto the court thinking of failure. When you start second-guessing everything, when you start playing with doubt ... I can't afford to play under those circumstances."
Anthony scored 21 points and the Knicks held on after blowing most of a 26-point lead to advance to the Eastern Conference semifinals against the Indiana Pacers.
Game 1 is Sunday in New York.
Iman Shumpert scored 15 of his 17 points in the second half, when the Celtics scored 20 straight points and cut a 75-49 deficit to four points. But Anthony made a 13-footer to give New York an 81-75 lead and followed with a 3-pointer -- his first since Game 3.
J.R. Smith converted a three-point play to restore the double-digit lead the Knicks had nursed most of the game.
"There's definitely a moment in that run that I was thinking, 'What are we doing, fellas?'" said Knicks center Tyson Chandler, who had nine points and 12 rebounds.
"It's such a great learning experience when you get a win. It's tough when you get a loss. We've got to grow from it. I'm glad it happened. I'm glad it happened in the first round."
Jeff Green scored 21 points for the Celtics, who had rallied from a 3-0 deficit in the series and had a chance, at home, to force a decisive seventh game.
No NBA team has advanced in the playoffs after losing the first three games.
Paul Pierce scored 14 points on 4-for-18 shooting, making one of nine 3-point attempts. Anthony also struggled from in- and outside the arc, going 7 for 23 from the floor and missing his first four 3-point attempts -- that was 19 in a row in the series -- before sinking the key basket with 1:43 to go.
"For him to miss all the 3s that he missed -- he hit the biggest one of the series and that's what counts," Knicks coach Mike Woodson said. "That's what I look at. When there are close games, I like to see who's going to step up and make plays, and he made the biggest play of the night."
"It's a major step for this organization, for our fans in New York who've been with us for many, many years," Woodson said. "I'm looking at the big picture and I'm only in this for one thing and that's to try to win an NBA title. We made a major step today, but we've got a long way to go."
Kevin Garnett had 15 points and 10 rebounds for the Celtics, who now face another offseason of talk whether to break up the aging core that won the franchise's record 17th NBA title in 2008 and returned to the finals two years later. Reserve Jason Terry scored 14 points -- the only points the Celtics got from their bench.
Rivers said he hasn't thought about his future, or the future of his aging stars, calling Garnett "as tough a competitor as I've ever been around" and Pierce "one of the greatest Celtics to ever play."
"He's done so much for this franchise," Rivers said. "We live in a day and time where guys change teams like socks. Paul has chosen to stay here throughout his career when he could have by all rights chosen to leave.
"He wanted to get it done here. I hope he's remembered for that. I hope he comes back."
A win on Friday would have made the Celtics the fourth NBA team to tie a series after losing the first three games. And it would have given them a chance to be the first in league history to win a series after trailing 3-0.
The Celtics called upon local history to rally them, playing highlights on the scoreboard from the Red Sox comeback against the New York Yankees after a 3-0 deficit in the 2004 AL Championship Series.
But Boston quickly fell behind 21-5 and trailed by double digits most of the way. The Knicks made it 75-49 with just under 10 minutes left before the Celtics scored the next 20 points, holding New York scoreless for 4:43 before Pierce threw the ball away and Shumpert took it in for an easy layup that made it 77-69 with 5 minutes left.
Avery Bradley made a layup, then Green hit a pair of free throws to make it a four-point game. It was 79-75 when Anthony made a 13-footer and then followed Pierce's missed 3-pointer with a 3 from the top of the key. He then stripped Pierce going to the basket, and Smith converted a three-point play at the other end -- Green fouled out on the play -- to make it 87-75.
Lines of fans were still waiting to get through the increased security at 7:20, about 10 minutes after the game started. ... Garnett's six points in the first quarter were twice as much as the rest of Boston's players combined as the Knicks took a 24-10 lead into the second quarter. ... The Celtics were 4 for 16 from the floor in the first and missed all six of their 3-point attempts. The Knicks also outrebounded Boston 13-7 in the period. ... Boston shot 23.5 percent in the first half. ... The Knicks made 5 of 6 3-pointers in the third quarter.