BOSTON -- Kevin Garnett made a statement against LeBron James and the defending Eastern Conference champions.
Ray Allen scored 20 points and Paul Pierce 12 in a game that was more intense than most preseason contests.
"Obviously you're a little jacked up because it's the Eastern Conference champions," Garnett said.
Allen hit a pair of 3-pointers during a 15-5 run to close the third quarter, turning a close game into a blowout. Boston led 86-73 after three.
It was the first matchup of what the Celtics hope could be a season capped with postseason games between LeBron James and Garnett.
James, who led the Cavaliers to the Eastern Conference title last season, finished with 17 points in 35 minutes. He played the entire first quarter, scoring 9 points on 3-for-7 shooting, including a crowd-pleasing driving scoop for his initial basket of the night.
After becoming one the game's elite players, James expects teams to play a little harder against him every time.
"That's been that way for a few years now," he said. "That's because of the type of player that I am. We're competitive every night."
Cleveland, which finished the preseason 1-5, hosts Dallas in its opener Wednesday. The Celtics, who were 4-3, open at home against Washington on Friday.
"The season starts Wednesday. We have to get it together or get blown out," James said.
Garnett, who played 33 minutes, threw a long pass to Eddie House for a breakaway layup that completed his triple-double with just less than 7½ minutes left.
Garnett, acquired from Minnesota in the offseason, hopes to lead Boston back into the playoffs. He matched James by playing the entire opening quarter, scoring 10 points.
"Overall there's not a lot to complain about. Kevin was fantastic," Boston coach Doc Rivers said. "Just the ball movement. It's hard to guard any team when the ball is moving like today."
The Celtics, who finished with the league's second-worst record last season, also picked up guard Allen on a draft-night trade with Seattle. Locally fans have called the two and Pierce "the new Big Three" -- hoping to see the success of the team's title-winning teams from the 1980s highlighted by Larry Bird, Kevin McHale and Robert Parish.
Pierce started the night with a drive and drew a foul on James. Each of the star players played more than 32 minutes each.
- Boston C Kendrick Perkins addressed the crowd before the game and prior to asking them for their support this season he opened with, "I'd like everybody to give it up for the Red Sox," which drew a big applause.
- Red Sox owner John Henry was seated courtside and was introduced to a standing ovation.
- The Cavaliers lost their final four preseason games.
- James and Pierce each took a hard fall after colliding midway into the third.