The C's trailed for much of the way and gave a sloppy, foul-filled effort all night, but they emerge with the 84-80 win thanks to a couple of big crunch-time stops.
Ray Allen leads the way for the Celtics with 22 points, among three other Celtics in double figures. Elton Brand gives the Sixers 16 points and 12 rebounds in defeat.
The C's now head to Orlando, where they're slated for a clash of Eastern Conference titans on Christmas Day.
Fourth quarter, 5.6 seconds, Celtics 84-80: That should just about do it. The Celtics get another big stop, and Ray Allen drains two crucial free throws.
Looks like the streak will live on.
Fourth quarter, 32.3 seconds, Celtics 82-80: Kevin Garnett comes up with a big steal, and the Celtics are now in position to bleed away the clock.
Paul Pierce calls timeout with six seconds on the shot clock, 32.3 on the game clock.
If they get a quick bucket here, it's almost game over. If not, the Sixers still might only get one shot at this thing.
Fourth quarter, 1:02, Celtics 82-80: Elton Brand fouls out.
Thaddeus Young will be manning the low post for the Sixers for this final minute.
The Sixers are in trouble, but far from dead. Especially with Shaq at the line.
Fourth quarter, 1:36, Celtics 82-78: Shaquille O'Neal comes up with a huge clutch rebound, and Paul Pierce drains a big, big shot to put the Celtics in control. They have a two-possession lead for the first time since … God knows when.
Doug Collins has called for a timeout. His Sixers have got some work to do now.
Fourth quarter, 2:17, 78-78: Paul Pierce hits two free throws, but Louis Williams strikes back with a running jumper. Tie ballgame again.
The Sixers continue to match the Celtics shot for shot. This one's going down to the wire.
Fourth quarter, 3:17, 76-76: Kevin Garnett ties the ballgame with two free throws.
He's 4-for-4 from the line now, and the Celtics as a team are 10-for-13. They've got to keep hitting their free throws down the stretch.
Fourth quarter, 4:33, Sixers 74-72: Paul Pierce just threw down a monster dunk in transition, and Shaquille O'Neal just swished two free throws.
Everything's going right for them now.
Can they ride this momentum?
Fourth quarter, 5:41, Sixers 72-68: Glen Davis dives for a loose ball and wrestles it from Andre Iguodala, forcing a jump ball.
Big Baby may be shooting 2-for-9 in this game, but his energy is keeping the Celtics alive.
Fourth quarter, 6:35, Sixers 72-68: Tony Battie and Paul Pierce were teammates seven years ago in Boston.
Now they're going head to head, and Battie is outscoring his old captain, 8-5.
Who could have seen that coming?
Fourth quarter, 8:15, 68-68: It's been a grinding, defensive game, and so far we've seen a grinding, defensive fourth quarter.
If the Celtics could get any kind of offense from Paul Pierce or Kevin Garnett, they could run away with it in these final eight minutes. But it's been a miserable night for the Celtics' two stars.
Fourth quarter, 10:11, 66-66: The Celtics have had their share of gripes about the officials in this one. But none of the Celtics' starters has five fouls yet; Elton Brand does.
The Sixers have been forced to give Tony Battie major minutes with Brand in foul trouble.
Remember Tony Battie?
If you do, I'm impressed.
End of third quarter, Celtics 64-61: Ray Allen and Von Wafer drain back-to-back 3-pointers to put the Celtics back in front at the close of the quarter, but their work is far from done.
For the second time this month, the Celtics are headed for a competitive fourth quarter with the Sixers. Who'd have thunk it?
The Celtics' 13-game winning streak is on the line.
Third quarter, 2:54, Sixers 57-56: The biggest difference in this game is obvious: The Celtics are 4-for-5 from the free-throw line, and the Sixers are 19-for-25.
Part of the foul discrepancy is the way this game has been called, as Doc Rivers would no doubt tell you. But the other part is the C's own laziness. They've got to get physical to grind this game out.
Third quarter, 5:46, Celtics 54-51: Tempers are flaring. Paul Pierce and Kevin Garnett have been chirping all night, at Sixers and refs alike, and they've both paid the price. Techs for both in the third quarter.
The C's have gotten fired up for this second half, and it's shown in both their play and their demeanor. That's a double-edged sword.
Third quarter, 6:41, Celtics 54-50: Now it's Nate Robinson's turn to drain the corner 3. The C's have leapt back into the lead, as Nate's jumper and a pair of Kevin Garnett free throws on the following possession stretch their edge to five.
It's a 14-2 Boston run, and it might not be over yet.
Third quarter, 8:08, Sixers 48-47: Paul Pierce is officially alive. The Celtics' captain scores five points in one minute, including a beautiful corner 3 to complete a 7-0 run and put the C's back in the game.
There's the Player of the Week. He's back in business now, and the Celtics have risen from the dead.
Third quarter, 9:35, Sixers 48-40: The Celtics still look rusty. They're a step slow on the 50-50 balls, and they still don't look as sharp offensively as the visiting Sixers.
The Sixers took a beating Tuesday night in Chicago. They're looking to get even now.
Halftime, Sixers 44-38: Paul Pierce was so bad in this first half that Doc Rivers yanked him for Von Wafer with a minute to play. Wafer scored more points in that minute (two) than Pierce has had all night (zero).
Pierce has played 20 minutes and is 0-for-6. Not a good encore performance for a guy who just won Player of the Week.
The Celtics are shooting 39.5 percent as a team, a far cry from their usual 50 percent clip.
The Celtics' Ray Allen leads all scorers so far with 13 points; Andre Iguodala and Jrue Holiday have nine each for the Sixers.
The C's need to wake up in the third quarter.
Second quarter, 2:26, Sixers 39-34: The Celtics have seven points in the last six minutes. Ray Allen continues to have a solid night, but the rest of the Celtics look pretty much dead.
Paul Pierce had a triple-double on Sunday. Now he's got zero points against the Sixers as we near halftime.
The C's need a kick in the pants.
Second quarter, 4:15, Sixers 35-30: Elton Brand is a solid four, maybe five inches shorter than Shaquille O'Neal, but he still manages to play outstanding defense on him. That's impressive.
Against a lot of younger defenders, Shaq is able to use his intimidation factor to bulldoze opposing centers. Not the case with Brand, who stands up to him.
The Sixers are on an 11-3 run.
Second quarter, 6:07, Sixers 31-30: It takes a 3 from Nate Robinson to finally break up a 7-0 Sixers run. The Sixers have reclaimed the lead in a flash, and it's been a solid two minutes since the C's had a good look at the basket.
The C's have had their way with most of those young, athletic teams this season, but the Sixers are a thorn in their sides. They just have too many weapons.
Second quarter, 8:02, Celtics 27-24: Flashy play from Avery Bradley — the Celtics' rookie guard steals the ball from Jrue Holiday in transition and dashes to the basket for a layup.
Good to see the new kid gain some confidence. He's a tremendous athlete who works hard on both ends — when he puts it all together mentally, he's going to be a heck of a player.
Second quarter, 9:24, Celtics 25-24: Andres Nocioni just knocked down an unexpected corner 3. He's a tricky one.
Remember when the Celtics almost traded for Noc? He would have been an interesting piece on the Celtics' second unit. Skilled player, good shooter.
End of first quarter, Celtics 23-17: The Celtics might have a pair of Hall of Fame big men in Shaquille O'Neal and Kevin Garnett, but right now they're winning this game in spite of them.
The C's are being manhandled on the glass — they were down 13-6 in rebounds a minute ago, and they've since cut the deficit to 13-9. Elton Brand and Spencer Hawes have five boards each for Philadelphia.
The biggest reason the C's lead this one is Ray Allen, who had a tremendous first quarter with 11 points on 5-of-8 shooting, plus two rebounds.
Jrue Holiday has nine points for the Sixers, who led for most of the first quarter before Allen and the C's pulled ahead.
First quarter, 2:28, Sixers 17-15: The quickest guy on the floor is 20-year-old Sixers point guard Jrue Holiday. Right now he's using that quickness to create open shots with ease, and it's killing the Celtics. He's 4-for-5 from the field, including a 3-pointer.
Holiday was shooting 8 for his last 34 going into this game. Coach Doug Collins talked before the game about Holiday's slump, saying he hoped it would end soon. It looks like Collins is getting his wish.
First quarter, 5:07, Sixers 11-10: Shaquille O'Neal just dove to the floor in pursuit of a defensive rebound, crashing into Elton Brand and forcing a jump ball in impressive fashion.
That's the kind of hustle you don't see every day out of the 38-year-old Shaq. That was a gift. Merry Christmas, C's fans.
First quarter, 7:10, Sixers 10-6: The Celtics have been really slow to establish any kind of post offense. They're settling for a lot of perimeter jump shots, and those shots are clanking the rim and rattling out.
Shaq was a beast in his first game back on Sunday, pouring in 11 points in the first six minutes. He's got just three in this one.
First quarter, 8:52, 5-5: The C's have had some execution problems early, with a couple of Nate Robinson turnovers and some bad shots from KG and Paul Pierce. But Shaquille O'Neal keeps them in the ballgame, getting a layup and a three-point play on a Spencer Hawes foul.
Not a good start for Hawes. First he fouls Shaq, then he gets a lane violation and gives Shaq a second chance to hit the free throw. Plus he's 0-for-1 from the field.
First quarter, 11:01, Celtics 2-0: Both teams trade stops to open, but a Kevin Garnett steal leads to a two-on-one fast break and a KG layup off a Nate Robinson assist. The C's have the early lead.
7:10 p.m.: Jermaine O'Neal will be out again on Wednesday night, but this time he's got a different excuse: the flu.
O'Neal's knee is fine now, but he's got a whole new ailment to keep him out of action against the 76ers on Wednesday. Doc Rivers says the Celtics' backup center "wasn't feeling great" at practice on Tuesday, and the illness has only worsened since.
Rivers remains confident that O'Neal will return on Saturday, when the C's take on the Orlando Magic on Christmas Day.
5:45 p.m.: Welcome to the TD Garden, where Jermaine O'Neal might make his return to the Celtics on Wednesday night, and he might not. It still remains to be seen.
O'Neal has guaranteed a return this week, but will it be Wednesday or Saturday, when the C's take on the Orlando Magic? We'll soon find out.
8 a.m.: The Celtics beat the Sixers last time they faced them, on Dec. 9, but only by the slimmest of margins.
With six seconds left and the C's trailing by one, it took a perfect lob pass from Rajon Rondo to Kevin Garnett to set up a game-winning layup and a 102-101 Boston triumph.
But when these two teams meet for Wednesday night's rematch, they won't see another Rondo lob. They won't see Rondo at all, in fact, as the C's point guard continues to rehab from a badly sprained ankle.
The Celtics just barely survived last time, and they'll be banged up once again heading into this one. This game will test the resolve of Doc Rivers' crew.
