BOSTON (AP) -- The New York Knicks must figure out how to finish off games.
Just watch the Boston Celtics .
The Celtics led for just 60 seconds in the second half until Ray Allen sank a go-ahead 3-pointer with 12 seconds left and beat the Knicks 87-85 in their playoff opener on Sunday night.
"Down the stretch we found a way to win," Paul Pierce said, "and that was because of our experience."
The Celtics won their NBA-high 17th championship in 2008 and lost in Game 7 of the finals last year to the Los Angeles Lakers . The Knicks, in the playoffs for the first time in seven seasons, last won a postseason game on Apr. 29, 2001.
"We can compete with them, obviously," New York coach Mike D'Antoni said. "They made big shots at the end. That's why they are who they are."
The Knicks ability to make those clutch shots may have suffered a blow when Chauncey Billups left with 51 seconds remaining with what he said was a strain in his left knee or thigh muscle. He and D'Antoni said they didn't know his status for Game 2 of the best-of-seven Eastern Conference first-round series on Tuesday night.
"We've got a couple of days and I'll just be treating it as long as I can," he said. "If I can get out there and help any, I'll be out there."
If he's not, Toney Douglas likely will start in his place.
On Sunday, it was Douglas who hit a 3-pointer with 39 seconds left that put the Knicks ahead 85-82. But after a timeout, the Celtics scored just one second later on an alley-oop pass from Rajon Rondo - who had 10 points, 9 rebounds and 9 assists - to Kevin Garnett.
"We just didn't communicate real well on that," D'Antoni said.
New York led 85-84 before Carmelo Anthony was called for an offensive foul for pushing Pierce with 21 seconds remaining.
"What I thought and what they called were two different things," Anthony said.
Boston coach Doc Rivers disagreed.
"Heck of a call to make," he said, "but it was the right call."
Rondo then lined up to inbound the ball but called timeout. The next time, Allen inbounded from just in front of the half-court line on the right side. He threw the ball to Pierce, then circled to the other side of the court, caught Pierce's pass and fired up the deciding basket.
"We've run that play many times," Allen said. "It's a play that has so many options and tonight I was just the option."
Pierce's pass set it up. His defense also shut down Anthony, who scored just 15 points and missed 10 of 11 shots in the second half, including a 3-pointer with 2 seconds to go. Anthony or Amare Stoudemire usually takes the shot with the game on the line, but Kevin Garnett guarded Stoudemire much tighter in the last few minutes.
"We've got to find a way to win down the stretch," Stoudemire said. "We had a great chance to win. We played well throughout the full 48 minutes. We just didn't quite close it out."
New York had the same problem against Boston on Dec. 15, when Pierce hit a jumper with .4 seconds left to put the Celtics ahead 118-116 at Madison Square Garden. Stoudemire then sank a 3-pointer, but it was waved off after officials determined that time had run out.
On Sunday, Stoudemire had 28 points and 11 rebounds for New York.
Allen led the Celtics with 24 points, Pierce added 18 and Garnett had 15 points and 13 rebounds.
Third-seeded Boston got a tough challenge from the sixth-seeded Knicks, who allowed 105.7 points per game during the regular season, third-most in the league.
"I'd like our offense to be better," Rivers said, "but the only way it will be is with (defensive) stops."
They didn't need a stop to set Allen up for the winning basket.
"Ray's the hero with the shot," Rivers said. "Paul's the hero with the pass. That's a great example of not playing hero basketball, just trusting what we drew up. And he made the shot."
And, with a chance to win the game, Anthony missed.
"We're very confident," he said. "We're a team that is going to look at this game and build off of it."
NOTES: During a timeout late in the second quarter, the crowd cheered when New England Patriots coach Bill Belichick was shown on the video scoreboard. He laughed and tipped his cap. But when the camera shifted to a spectator wearing a No. 1 Knicks jersey in the row behind him, the fans booed. ... The Knicks have lost their last three playoff series since beating the Miami Heat in seven games in the Eastern Conference semifinals in 2000. ... The Celtics are expected to be without center Shaquille O'Neal for Game 2. He missed the last six regular-season games and the playoff opener with a sore right calf.