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SAN ANTONIO -- The Boston Celtics finally got a big win and their big man back. They may also reclaim the No. 1 seed in the Eastern Conference.

And the San Antonio Spurs, at this dismal rate, may give first place in the West away.

Rajon Rondo had 22 points and 14 assists, center Jermaine O'Neal returned from knee surgery, and the Celtics ended a miserable March by not slipping further from first in the East, beating the slumping Spurs 107-97 on Thursday night.

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Paul Pierce added 21 points and 11 rebounds, and Kevin Garnett scored 20. The Celtics won for just the second time in five games and, ending the month at 9-7, moved within two games of Chicago for the No. 1 playoff seed with eight games to go.

"This is a good place to try and gather some momentum," Pierce said. "You talk about the team with the best record. What better place to get back on track than here?"

Yet these days, San Antonio's luster isn't what it used to be.

The Spurs lost their fifth straight -- their longest skid all season -- and the timing couldn't be worse. San Antonio has seven games left but is in danger of falling out of first place after comfortably being No. 1 in the West all season.

San Antonio's woes have renewed hopes the Los Angeles Lakers and Dallas have of taking the top spot. The Lakers are 2½ games back after beating the Mavericks on Thursday night.

"Of course we want to be No. 1. We don't want to give it way just because we like being underdogs," Spurs guard Manu Ginobili said. "We want to win it. We put ourselves in an unbelievable situation."

Tony Parker led the Spurs with 23 points. Tim Duncan returned after missing the last four games with a sprained ankle and finished with 20 points and 13 rebounds.

The Celtics celebrated the return of their own big man: O'Neal. The 14-year veteran played for the first time since January after having arthroscopic surgery on his left knee. He scored five points in 11 minutes and hit his only two shots.

He turned his last into a three-point play after getting fouled, a play that swung the momentum back to Boston after the Spurs had gotten within seven early in the fourth.

O'Neal said he felt winded at times and said he was shocked at the pace of the game. It was just the 18th game for O'Neal this season.

"We need him back," said Celtics coach Doc Rivers, alluding to his depleted frontcourt that is still without Shaquille O'Neal. "And we need the minutes."

Glen Davis scored 16 points as Boston had four players in double figures.

Nenad Krstic injured his knee during the game, and according to Rivers, will have an MRI on Saturday and will miss games on Friday and Sunday.

"I don't know," Rivers said when asked about the severity of the injury. "He's out, obviously this weekend, then an MRI. That's as far as I'm going to go."

The Celtics broke open a tie game at halftime behind a 12-0 run in the third quarter. The Spurs never got closer than six after that.

The Celtics arrived in San Antonio after losing to Indiana, Charlotte and Memphis in three of their last four games. Two weeks ago, Boston (52-22) was tied for first place in the East.

Miami has also crawled back into contention for first, sitting a half-game behind Boston, but a big win against the toughest opponent they've seen in weeks kept the Celtics ahead of the Heat.

Then again, the Spurs aren't looking so tough lately.

San Antonio (57-18) didn't panic after losing four games with Duncan sidelined. But not even its starting five back and healthy could help the Spurs stop their season-worst skid.

The Spurs had nine losses at the All-Star break. They've dropped more than half that number of games in the past week alone.

"It happens to everybody. And this is about the worst time it could happen, at the end of the year," Spurs coach Gregg Popovich said before tipoff. "If it has to happen, you want it to happen 30 games in so you can get back and recover. So we got to step on it."

Ginobili, who sat out Monday's loss against Portland with a left quad contusion, had nine points on just 4-of-13 shooting. Richard Jefferson added 14 points.

Game notes

Information from The Associated Press was used in this report.