BOSTON - Rajon Rondo didn't get his normal game-day nap Saturday as sleep was hard to come by. And early on against the 76ers, he and his teammates indeed seemed a bit weary as the Sixers grew a lead of 13 points in the first half.

But Rondo awoke in a big way, posting 13 points, 17 assists, and 12 rebounds in leading the Boston Celtics to a 92-91 series-opening victory at TD Garden.

In the opening game of this playoff run, the Sixers watched as point guard supreme Derrick Rose fell to the floor, writhing in pain after tearing a ligament in his knee. Without the NBA's reigning MVP, the Chicago Bulls certainly suffered and ultimately fell to the Sixers in six games.

On Saturday, Rondo put on an MVP-type performance. He continuously went wherever he wanted on the court, and when shots were missed he was able to corral offensive rebounds, finishing with a game-high five.

"I didn't get a nap today, so I didn't know what to expect," he said. "I was struggling, so I tried to do the intangibles to help my team."

From the beginning of this playoff run, which surprisingly reached a second round after the Chicago series, 76ers coach Doug Collins has spoken of the importance of his young team seeing the ball go into the basket early and often.

That is exactly what happened on Saturday as the Sixers, who averaged 22 points in the first quarter against the Bulls, dumped 28 on the Celtics and opened up leads as big as 13 in the first half.

But the Sixers fell victim to the Celtics' top-ranked defense in the fourth quarter. They produced four nothing-gained offensive possessions, and the Celtics sealed the win.

"There were ebbs and flows," said Collins. "Rondo was spectacular, and when it's all said and done we had a great chance to get this game. We had four really bad offensive possessions that really hurt us."

Those possessions were the turning point of the mostly tight game. With fewer than three minutes remaining, Lou Williams missed a contested three-on-one fastbreak layup with the Sixers leading by 84-83. The Celtics then got out on the run, and Rondo fed Kevin Garnett (29 points, 11 rebounds), who converted a layup and was fouled by Spencer Hawes. The free throw gave the Celtics an 86-84 lead with 2 minutes, 52 seconds left in the game.

After a turnover by Williams, Garnett drained a long jumper, and the Celtics were able to close out what could have been a tone-setting series win for the Sixers.

"That one hurt because I think we did a lot of good things," said Williams, who finished with nine points. "I think we played well enough to win the basketball game. We had some costly turnovers there. Under the four-minute mark, shots didn't go in anymore. But even after all that, we still battled back and put ourselves in a great position to win. That will sting a little bit."

While the shots fell for the Sixers in the first half, it was also easy to see what their defensive scheme seemed to be for the series - double team Paul Pierce (14 points) as much as possible and live with the likes of Brandon Bass, Avery Bradley, and Rondo throwing up jump shots. Like the offense, that worked well. Pierce scored just two points in the first half, and the other three combined to go 4 for 17.

That helped the Sixers blow out to a lead of 45-32 with 3:44 left in the first half. That's when the Celtics appeared to get their late wake-up call. Over the next 10 minutes of the game, they used a 21-4 run to grab a 51-49 lead midway through third.

The Sixers, however, responded with an 8-0 run of their own later in the quarter and still led going into the fourth by 71-67.

For much of the third quarter Collins put Lavoy Allen and Hawes on the floor together, a pairing rarely seen. But it worked in clogging the middle, where the Celtics had been driving the ball earlier in the quarter.

It was also done out of necessity. Thaddeus Young, who sprained his right ankle in the first half, didn't get off the bench.

Allen, a Temple product, didn't see a minute of action in the Chicago clincher but came off the bench to score 12 points and grab six rebounds.

"They hit us with that finish at the end [of the first half]," said Collins. "They went to a smaller lineup and we were fine. But we missed three layups in that stretch. I thought we had some stretches where we made some poor decisions. But we've got to give the Celtics defense a lot of credit with that."

Andre Iguodala, the star on Friday after his two foul shots with 2.2 seconds remaining gave the Sixers the Chicago series, aggressively attacked Pierce on the offensive end all night and finished with 19 points.

Evan Turner scored 16 and grabbed 10 rebounds for the Sixers, while Hawes had 15 and eight.

Contact Bob Cooney at cooneyb@phillynews.com.