BOSTON — A playoff berth would have been cause for celebration last season. This year, it's just the first step for the Boston Celtics.

The Celtics became the first NBA team to clinch a spot in the postseason, an accomplishment they barely noted Wednesday night after beating the Detroit Pistons 90-78.

"We are trying to get home-court advantage," said Kevin Garnett, who had a season-high 31 points, scoring five straight after the Pistons tied it at 69 in the fourth quarter to help Boston beat its closest competitor in the Eastern Conference.

"All of these games are huge for us."

The Celtics missed the playoffs the last two seasons, but the arrival of Garnett and Ray Allen has raised expectations for the NBA's most decorated franchise. So even though Wednesday's victory ended their playoff drought, it was more important because it gave them a 2-1 victory in the season series with Detroit.

If the Pistons (44-17) tie the Celtics (47-12) in the standings and meet them in the playoffs, Boston would have the home-court advantage. That could be crucial, considering the way the teams banged into each other the first three times they played this season.

"Any time you play another elite team it will be a playoff atmosphere. All three felt like that," said Chauncey Billups, who scored 23 points, going 14-of-15 from the line for Detroit. "It was very physical. That's what we like to do. That's great basketball and all games should be like that."

The idea gave Celtics coach Doc Rivers pause.

"I don't want to think about that," he said. "But the way I look at it is if we do see them again, it's only a good thing."

Kendrick Perkins had a career-high 20 rebounds to go with his 10 points, and Rajon Rondo had 16 points to help Boston win its sixth consecutive game. Paul Pierce scored 15.

Rasheed Wallace also scored 23 for Detroit, Richard Hamilton scored 15 and Tayshaun Prince had 10 rebounds, seven points and five assists.

The Pistons never led, falling behind 17-3 off the opening tip and working their way back to a 69-all tie on Tayshaun Prince's put back for the first basket of the fourth quarter. But Garnett made a free throw, a jumper and a layup and, after Detroit cut it to 78-77, the Celtics scored 12 in a row.