Ray Allen hit the decisive three-pointer with 12 seconds remaining on Sunday as Boston rallied to beat New York 87-85 in the first game of their NBA Eastern Conference first-round playoff series. New York led 85-84 before the Knicks\' Carmelo Anthony was called for an offensive foul for pushing Paul Pierce with 21 seconds to play. Allen, who led the Celtics with 24 points, then sank the key shot from behind the three-point arc. After Anthony\'s foul, Rajon Rondo lined up to in-bound the ball for Boston but called timeout. Then Allen instead in-bounded from just in front of the half-court line. He tossed the ball to Pierce, moved to the opposite side of the court and caught a pass from Pierce and put up his three-pointer. \"Ray\'s the hero with the shot,\" Boston coach Doc 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.\" The Knicks headed downcourt, but Anthony missed a long three-point attempt with two seconds remaining, Anthony finishing 1 for 11 from the field in the second half. Amare Stoudemire had 28 points and 11 rebounds for New York, and Anthony finished with 15. The Celtics, who won their league-leading 17th title in 2008, are trying to get back to the NBA finals after falling to the Lakers in the championship series last season. They host game two on Tuesday. Knicks point guard Chauncey Billups said he was not sure if he would be ready to play on Tuesday after leaving the game with 51 seconds left with a strained left knee or thigh muscle. \"I went to the basket and as I took off on my leg it just kind of buckled on me,\" Billups said. \"I\'m in a lot of pain right now, but that\'s to be expected.\" The Knicks are in the playoffs for the first time in seven years. The contest was the only Eastern Conference clash on Sunday\'s slate. A Stoudemire dunk over Kevin Garnett and Jermaine O\'Neal gave the Knicks an 82-78 lead, but he had only one more touch the rest of the game. \"In the playoffs, you have to take these games and learn from them,\" Stoudemire said. \"We can\'t let this game beat us Tuesday.\" Anthony was encouraged rather than discouraged, despite the defeat. \"We did some things great for the most part of that game,\" Anthony said. \"I\'m excited about this series, though.\" Pierce finished with 18 points for Boston and Garnett added 15 points and 13 rebounds as the third-seeded Celtics snatched the victory from the Knicks. Pierce did a superb job of guarding Anthony, giving him few clear looks at the basket. However, he said the Celtics would have to improve. \"It\'s all about our defense and execution down the stretch,\" Pierce said. \"We can\'t rest on this victory because by no means was this our best basketball.\"