BOSTON, April 5 (Ticker) -- Shaquille O'Neal missed another game and Kobe Bryant missed a lot of shots.

With O'Neal on the bench and Bryant off his game, the Los Angeles Lakers suffered their worst loss of the season, a 99-81 setback to the Boston Celtics, who clinched their first playoff berth in seven years.

"That was a good way to celebrate making the playoffs," Celtics coach Jim O'Brien said.

O'Neal, bothered all season by an arthritic toe, sat out his second straight game with a sprained right wrist. The superstar center's absence clearly was felt as Los Angeles managed just 24 points in the paint.

NBA TV highlights from Lakers-Celtics: 56k | 300k Paul Pierce and the Celtics were 4-0 against the NBA's L.A. teams this season.

Bryant, who nearly picked up the slack for Shaq in Wednesday's loss at New Jersey, was not up to the task in this one. He made just 5-of-25 shots as the Lakers were a season-low 34 percent (28-of-82) from the field.

"It was a tough shooting night," Bryant said. "The ball didn't want to stay down. They were pretty wide-open looks, but they weren't staying down."

"There are some nights you can't shoot the ball," Lakers coach Phil Jackson added. "Their defense kept us on the outside. We had open looks, but we didn't make them. We didn't have any second-chance opportunites in the lane."

Los Angeles held its only lead at 2-0 and trailed by as many as 23 points. It tied a season low for points in a half (33) and set a new low for points in a game.

The Lakers also lost by 18 points at Minnesota on January 11 (120-102) and at San Antonio on March 20 (108-90). They dropped to 7-8 without O'Neal this season.

Paul Pierce scored 33 points for the Celtics (44-32), who are in the playoffs for the first time since 1995, the year they closed Boston Garden. The Celtics swept the Lakers for the first time since the 1991-92 season.

"Our goal is to finish out the season with the best record as possible," Pierce said. "We're still trying to secure the home court (for the first round)."

Pierce pushed his season total to 2,005 points, joining John Havlicek and Larry Bird as the only Celtics to put together 2,000-point seasons.

Pierce scored 17 points in the first half, when Bryant made just 4-of-14 shots. The Lakers trailed by as many as 12 points before closing to 39-33 at intermission.

"We had 23 points for the longest time," Lakers forward Rick Fox said. "I think it was 33 at the half. On the road, it's not going to put you in a position to win, not against a good defensive team like the Boston Celtics."

The Celtics opened the third quarter with a 10-1 run sparked by Kenny Anderson, who came off the injured list earlier in the day. But Bryant, still struggling from the field, made 10 free throws in the period as the Lakers closed to 59-54 with 1:30 left. "He struggled through the third quarter and he still got us back in the ballgame," Jackson said.

"Kobe had a poor first half and we knew that he'd probably try and come out without a lot more aggression in the second half, so we just wanted to come out with a little aggression of our own," Pierce said.

In the fourth quarter, the Lakers' poor shooting finally caught up with them. A 3-pointer by Antoine Walker opened the period and gave the Celtics a 69-58 lead. The Lakers got no closer.

"The start of the fourth quarter, we're down six, they hit two threes in a row and push the lead up," Bryant said. "They hit a couple of more after that and it got pretty ugly from there."

"They came out and really laid it on us in the fourth quarter," Jackson added. "They saved their best for last. We couldn't seem to mount a rally to stay with them in the fourth quarter."

Walker had 20 points, nine rebounds and eight assists and Anderson had 12 points and nine assists for the Celtics, who shot 45.5 percent (40-of-88) and held a 49-41 rebounding advantage. Tony Battie swept a career-high 15 boards.

"I'm happy to be back with my teammates, running and having fun," Anderson said.

"He's pretty much our only pure point guard on the team and when you've got him back, everything's going to flow more smoothly," Walker said of Anderson. "He's great at controlling the game. It's good to have him back."

Fox scored 13 points for the Lakers (53-23), who fell 2 1/2 games behind Sacramento in the race for the best record in the Western Conference. They also are percentage points behind Dallas.