CLEVELAND -- The lopsided difference on the scoreboard indicated the game was probably over. LeBron James wasn't convinced.
The Cavaliers, who trailed 11-0 to open the game and 25-6 in the first quarter, were down by 25 points in the third period and still trailed 82-63 with 10:16 remaining before storming back.
"We could have easily packed it up but that's not who I am," James said. "Any time I'm on the court it doesn't matter how many points we're down, we always have a chance to win."
With their superstar driving to the basket nearly every time he touched the ball, the Cavaliers outscored the Celtics 34-17 in the fourth and staged one of the biggest comebacks in franchise history.
The team doesn't have complete play-by-play records, so it's impossible to know if the Cavs have overcome any greater deficit.
This one has to be up there.
"We had no business winning that game," Cavaliers coach Mike Brown said. "We willed our way to a win."
James, who came in shooting just 63 percent on free throws, went 19-of-23 from the foul line but missed a pair of foul shots -- one on purpose -- with 1.2 seconds remaining. James was short on his first attempt, and intentionally missed on his second try but the ball failed to hit the rim.
As wine-and-gold streamers and confetti fluttered from the rafters, the final score was announced over the loudspeaker as Cavaliers fans danced in the aisles. However, Celtics and coach Doc Rivers quickly argued that James' miss was a violation and wanted the ball.
The officials huddled briefly near halfcourt and gave it to Boston. In the meantime, most of Cleveland's players had already gone to the locker room and had to be summoned back to the bench.
Boston threw a high inbounds pass to Paul Pierce, who caught it but had his potential game-winning 3-pointer rattle off the rim.
"It looked very good, too," said James, who added eight rebounds and five assists in 44 minutes of Cleveland's sixth straight victory over Boston.
Sasha Pavlovic had 14 points and made two crucial 3-pointers during Cleveland's frantic rally.
Pierce scored all of his 19 points in the second half and Sebastian Telfair, who was briefly hospitalized on Friday with shortness of breath, had 15 for the Celtics.
"We just stopped attacking," Boston coach Doc Rivers said. "We attacked for three quarters, then we stopped. We stopped playing. You can't do that. You have to play through the clock and we didn't."
Boston didn't dress Wally Szczerbiak (back), and Theo Ratliff (back) and Al Jefferson (appendectomy) were both sidelined with injuries but the Celtics still managed to take a 76-60 lead into the fourth.
Trailing 82-63 after Tony Allen's three-point play, the Cavaliers began chipping away at Boston's big lead.
James converted a three-point play, Pavlovic hit a jumper and Damon Jones knocked down a 3 from the left wing to make it 82-71 with 8:36 left. After a Boston turnover, Pavlovic hit another 3-pointer and James fed Anderson Varejao underneath to get Cleveland within 84-78.
Cleveland's defense forced Boston into a shot-clock violation and Pavlovic's 3-pointer brought the Cavs to 86-85. Larry Hughes then blocked a shot and scored on a high-arching shot in traffic as the Cavaliers took their first lead at 87-86.
"It seemed like we waited for time to run out instead of punching back in the fourth quarter," Pierce said. "They willed the game away from us. We thought a 16-point lead was good enough, but it wasn't."
Boston missed its next two shots, and on Cleveland's next trip, James drove the left side and had his headband ripped off by Kendrick Perkins while hitting a left-handed layup. James completed the three-point play to make it 90-87 and the Cavs survived the crazy final sequence for the win.
Pierce didn't score in the first half. He didn't have to as Boston opened a 14-point lead at the break thanks to 26 percent shooting by the Cavaliers.
Pierce scored his first point on a technical foul with 9:49 left in the third quarter, and then Boston's sharpshooter went on a tear. He dropped two medium-range jumpers followed by a pair of 3s to give the Celtics a 65-40 lead.
- George Mason coach Jim Larranaga and his team attended the game. Earlier, the Patriots opened their season with a 79-74 win at Cleveland State.
- Boston was just 5-of-23 from the field in the fourth.
- The Cavaliers shot 17 percent (4-of-23) in the first, their poorest outing in the first 12 minutes since shooting 3-of-18 in a March 2002 game against Toronto.
- Celtics radio announcer Cedric Maxwell was caught off guard by the Cavs' pyrotechnic pregame display and nearly jumped out of his seat following a loud fireworks explosion.