NEW YORK — Another horrific second-half drought. Another very bad result for the Celtics .
Carmelo Anthony scored 34 points, NBA “Sixth Man of the Year” J.R. Smith added 19 while Raymond Felton  (16 points) chipped in with several big drives to the basket, as the Knicks beat the Celtics, 87-71, in Game 2 Tuesday night at Madison Square Garden. The series now shifts back to Boston with the Celtics, down 0-2, facing a virtual must-win on Friday night at TD Garden.
Paul Pierce  scored 18 while Kevin Garnett  added a double-double (12 points, 11 rebounds) for the Celtics, who suffered through another horrendous second-half drought, blowing a nine-point lead late in the first half to fall two games down to the Atlantic Division champs. After scoring just 25 points in the second half Saturday in Game 1, and eight in the fourth quarter, the Celtics scored just 11 points in the third quarter and finished the second half with just 23 points, the lowest second-half scoring output in team playoff history since the introduction of the shot clock.
The Celtics appeared to have momentum early. They built a 20-15 lead in the first quarter on Jason Terry ‘s first field goal of the series. After going 0-for-5 in Game 1, Terry’s 3-pointer was the first of three treys in the first half. But the Knicks then ran off the next 12 points, closing the first quarter on an 11-0 run, thanks in part to a troubling turn at the end of the period.
Smith hit a jumper with 6.8 seconds left to put the Knicks up 23-20. Pierce committed a turnover and the Knicks found Smith, who drained a 36-foot three at the buzzer, putting the Knicks up 26-20.
After the Knicks went up 27-20, the Celtics answered with the next 11 points as Terry led a resurgent bench. When Pierce hit a 12-foot turnaround with 1:02 left in the second quarter, Boston had its biggest lead, 48-39. That would be the last time the Celtics had control.
The Knicks scored the final three points as another Pierce turnover kept Boston from building momentum at the half. As hot as the Celtics were in shooting 11-of-18 from the field in the second quarter, the Knicks were just as cold, making just 4-of-17 shots.
Those three points at the end of the first half started a remarkable turnaround for New York. Iman Shumpert hit a pair of threes to open the third quarter as the Knicks exploded on a 29-6 run. Before the third quarter was over, the Knicks had outscored the Celtics 32-11, building their lead up to 15, 74-59, heading into the fourth. It was a complete role reversal for the two teams in the third, as the Celtics made just 4-of-18 while the Knicks were blazing hot, converting 12-of-17 from the field.
Pierce rattled in a three with 9:47 to cut New York’s lead down to 11, 76-65. Jordan Crawford hit a jumper over Steve Novak with 9:15 left and Boston trimmed the deficit to single digits, 76-67.
Following a Knicks timeout, Anthony hit a shot over Garnett with 8:56 left to put the Knicks up, 78-67. After two Garnett free throws, it was Anthony again with a jumper. The Garden crowd exploded when Felton fed Smith with 7:52 left for an alley-oop dunk putting New York ahead, 82-69. After Garnett picked up his fifth foul with 6:28 left, Felton hit a mid-range jumper at the free throw line to put New York up, 84-69.
Pierce and Garnett came out with just over four minutes left as the Celtics conceded their second straight playoff loss in New York. With the Knicks up, 2-0, the series shifts to Boston for Game 3 Friday night at 8 p.m. at TD Garden. Game 4 will also be played in Boston (Sunday, 1 p.m.).
For more from Mike Petraglia with the Celtics in New York, visit the Celtics team page at weei.com/celtics .