The Detroit Pistons' problems started early in Game 6 of their NBA Eastern Conference semifinal series tonight against the Boston Celtics. First the game clock wouldn't start, then the basketball used in the opening moments wouldn't bounce properly.

Soon, it was obvious that the team's offense was also out of kilter. After shooting 39 percent in the first half, the Pistons rallied briefly but lost to the defending champions, 123-113, and were eliminated from their playoff series, 4-2.

The Pistons' biggest problem was the same one that hindered them throughout the series: overreliance on one player. Tonight that player was Isiah Thomas, who had 37 points, 12 rebounds and nine assists. In the time it took the Pistons to find him, though, the magic of earlier heroes, such as Vinnie Johnson and Bill Laimbeer, had vanished.

Meanwhile, the Celtics were playing team basketball, so much so that they had no individual hero. Robert Parish, who shot only four times in a 130-123 victory in Game 5, had 24 points and 13 rebounds tonight.

Many of his points came just when needed, but then again, so did many of Dennis Johnson's 22, Kevin McHale's 20, Larry Bird's 17 and substitute Scott Wedman's 17.

"We gave Scott the game ball tonight," Boston Coach K.C. Jones said. "Larry had a difficult time and missed the ocean on his shots, so I took him out and put Scott in. He responded and did exactly what we were looking for."

Detroit Coach Chuck Daly could only shake his head and say: "They're just a great team with a lot of great weapons. We fought them tough, but they had too much for us."

That was obvious the entire fourth quarter, when the Celtics forced the ball inside against their smaller opponents, who had to foul. The Celtics really won the game at the foul line, making 13 of 17 that last quarter.

Down by 105-95, Detroit rallied to 105-101, but the Celtics, showing their strength inside, scored their next 11 points from the line.

"I had a smaller man on me," Parish said, "so I was posting up and, once I got it going, they kept getting me the ball. We came in here last week wanting to get two, but it didn't work out. We got the job done tonight, though."

But as Thomas admitted, the Celtics didn't get it done without lots of help from the Pistons. Besides shooting 46 percent, Detroit lost the ball 19 times, handing the Celtics 28 points.

"Turnovers definitely hurt us . . . " Thomas said. "Tonight, they were a better team. Basketball has a way of giving turns; tonight it was theirs."

It definitely wasn't the Pistons'. They played frantically, but tensely, in the early going, accomplishing little. Passes bounced off open hands and, on occasion, off faces.

Lacking inside strength, they shot from outside and tried to play one-on-one. That worked in Games 3 and 4 here last week, but not tonight.

Down by 63-52 at halftime, the Pistons rallied, surprisingly enough, by abandoning plays and just passing the ball around. The coach of the Cleveland Cavaliers, George Karl, was a spectator and approved.

"The passing game relaxes you," he said. "Instead of thinking about executing plays, you're just reacting. It's a way of just going out and playing ball."

That's exactly what the Celtics will do Sunday, when the conference finals begin in Boston against the Philadelphia 76ers. "There aren't many upsets in a seven-game series," Daly said. "If we had played an above-average game I think we would have won. It's hard to get through 13 big games, but I think Boston is capable." 76ers Have Conflict United Press International

NEW YORK, May 10 -- A rock concert scheduled for Saturday May 18 at the Philadelphia Spectrum could force the 76ers to play their first home game of the Eastern Conference finals somewhere else, perhaps as far away as the Meadowlands Arena in East Rutherford, N.J., where the New Jersey Nets play their home games.

"We don't know if there is going to be a Game 3 here," a spokesman for the Spectrum said.

Other possible alternative sites are the Philadelphia Convention Center and the Philadelphia Palestra and the Meadowlands, the home court of the New Jersey Nets.

John Nash, assistant general manager of the 76ers, confirmed that the team is considering playing somewhere other than the Spectrum.