With Paul Pierce, Kevin Garnett and Ray Allen sitting out to avoid possible injury, the lack of defense and excitement had spectators moving toward the exits midway through the fourth quarter.
The game began as a possible first-round preview if Milwaukee won and Miami lost to New Jersey.
Rajon Rondo had 21 points and 15 assists for the Celtics, who lost for the seventh time in 10 games.
Milwaukee finished with a 46-36 record, a 12-game improvement over last season. That's the biggest gain in the Eastern Conference as the Bucks reached the playoffs for the first time in four seasons.
The Celtics finished at 50-32, their worst record in three seasons. They won the NBA title in 2008 but were eliminated in the Eastern semifinals in 2009.
On Wednesday night, the Celtics took their last lead, 72-71, on a 3-pointer by Michael Finley with 4:43 left in the third quarter. Then the Bucks finished the quarter with a 17-6 run that gave them an 88-78 lead going into the fourth. Milwaukee led by at least 10 points the rest of the way.
The game had none of the defense — or intensity — of Boston's 105-90 win at Milwaukee last Saturday night in which the physical play picked up in the final 3:32.
Kurt Thomas complained to referees when he felt he was fouled by Glen Davis but didn't get the call, then got a flagrant foul when he threw Davis to the floor. Davis got a technical foul when he immediately bumped Thomas. On the next possession, Pierce and Stackhouse got tangled up and Stackhouse was called for a foul while holding Pierce.
Bucks coach Scott Skiles argued the call and was given a technical foul and automatic ejection.
It was only 76-74 when Ersan Ilyasova hit three straight Milwaukee baskets, a 3-point bank shot, a 19-foot jumper and another 3-pointer. Ilyasova finished with 15 points. All Boston could manage in that stretch was a 3-pointer by Rasheed Wallace as the Bucks led 84-76 with 56 seconds left in the period.
For the Celtics, Marquis Daniels scored 13 points and Shelden Williams and Nate Robinson added 12 each.
Notes
The Bucks snapped a two-game losing streak. … Guard Oliver Lafayette had seven points in his first game for the Celtics after playing for Fort Wayne in the NBA Development League. … Boston's regular center Kendrick Perkins sat out the game to avoid picking up his 16th technical foul, which might have brought a one-game suspension for either the playoff opener or next season's first game.