NEW YORK (Reuters) -- Philadelphia's fragile playoff hopes took another jarring body blow on Friday with a 109-99 loss to the Boston Celtics.

The 76ers efforts to secure an Eastern Conference playoff spot have come undone down the stretch, losing three straight and 13 of their last 17.

They remain in ninth place, one game behind the Chicago Bulls for the final playoff spot in the East.

Philadelphia lost at home to Chicago earlier this week and face the Bulls in Chicago in a game with mammoth playoff implications.

"We just can't seem to play with any consistency lately," a dejected Philadelphia coach Maurice Cheeks told reporters.

Allen Iverson led the Sixers with 37 points, but he questioned his team's work ethic when talking to reporters after the game.

"We don't seem hungry," Iverson said. "We don't seem like we want to make it to the playoffs. "I hope it's not that anybody's given up on us. I haven't."

The Sixers (34-41) got off to a quick start, scoring 34 points in the first quarter and taking a 59-55 lead at the half.

But poor defense, which has plagued the team all season, again reared its head in the second half as the Celtics shot 53 percent from the floor, outscoring the Sixers 26-17 in the third quarter to take control. "We were playing a team that was obviously playing desperate and you could see that play in them," Boston coach Doc Rivers told reporters. "We were loose and we played loose."

The Celtics have already been eliminated from the East playoffs.

Paul Pierce had 33 points, 12 rebounds and six assists while Gerald Green added 17 points off the bench.

Chris Webber had 18 points and 11 rebounds for the Sixers.

In San Antonio, Dirk Nowitzki scored 30 points as the Dallas Mavericks edged the Spurs 92-86 in a showdown between the top two teams in the Western Conference.

San Antonio (58-18) saw its lead in the Southwest Division cut to one game over Dallas (57-19), with both teams having six games left to play.

Josh Howard added 22 points for the Mavericks, with 20 of them coming in the first half.

Manu Ginobili led the Spurs with 22 points, but Tim Duncan was held to just 13 points, while Tony Parker had just 10.

In Orlando, Hedo Turkoglu had 26 points and seven rebounds as the Magic edged the short-handed Detroit Pistons 89-87.

Jameer Nelson hit two key baskets in the final seconds for the Magic, who won their ninth straight home game and snapped Detroit's six-game winning streak.

Chauncey Billups led the Pistons with 25 points and eight assists, but they were missing Richard Hamilton, who left the team after a death in his family.