Sometimes in the NBA -- land of homecourt advantage, of momentum and adjustments, of ebb and flow -- it is hard to tell who won, even after the final score is on the board.

The Los Angeles Lakers, after their opening victory over Philadelphia in the NBA finals here, were content that -- in Coach Paul Westhead's words -- "we established some semblance of order. It's so common to see a team play all year for the homecourt advantage, then throw it away in the first game."

The 76ers, after the 109-102 loss, did not behave like a team that had lost one iota of its confidence. On the contrary, the Sixers had considerable justification for seeing good things amid the frustrations of this splendidly exciting afternoon.

"If you shoot three for 20 (as the 76ers did in the third quarter), it's tough to beat a high school team," said Philadelphia Coach Billy Cunningham. "I was pleased with the way we hung in, then made a decent comeback. Basically, we did what we wanted to do."

The Lakers came close to playing an ideal game this afternoon, yet they needed a fourth-quarter tightening of the belt -- after a 16-point lead had shrunk to four -- to pull away.

"We played Julius Erving perfectly," said Westhead. Doctor J still scored 20 points.

Six center Darryl Dawkins fouled out after only 18 minutes of playing time. But 7-foot-1 power forward Caldwell Jones forced Kareem Abdul-Jabbar to take some extremely tough shots for his 33 points.

"Kareem took the shots I wanted to force him to take," said Jones. "When he started hitting them, I said, 'It's going to be a long game.'"

The Lakers could take satisfaction that, after setting an NBA field goal percentage record of .529 in their 60-win season they shot .539 against the Philadelphia team whose defense held Boston under 100 points five straight games.

On the other hand, Philly's deep front line had 13 blocked shots and its quick hands produced a dozen steals. All eight of the players on whom it regularly depends had fair to good opening efforts. How many 16-for -56 second-half shooting games can these springting Sixers have?

The Lakers, by contrast, looked just a shade thin is you looked closely. Big forward Jim Chones had just three points and barely seemed to be in the game. Fleet sixth-man Mike Cooper had just two points (one-for-seven shooting) and, as Dr. J. noted, "If Cooper doesn't get his points on the fast break, he doesn't get any."

While Philly looked eight deep and organized, the Lakers only had one minor character -- Mark Landsberger with 10 points -- who could support their big four of Abdul-Jabber, Magic Johnson Norm Nixon and Jamaal Wilkes, all of whom averaged 17.5-points or more in the regulr season.

That quartet turned in trademark performances. Wilkes, with 20 points, seven rebounds and six assists, seemed effortless and invisible. Johnson, as usual, did a bit of everything. In fact, his incredible blind over-the-shoulder pass as he was barreling out of bounds (which assisted Nixon on an easy jump shot) gave the Lakers a 98-89 lead and wilted Philly for good.

Nevertheless, what happens if one of those central four has a bad night? Who takes up the slack? What happens if Dawkins doesn't get in foul trouble and Erving isn't "held" to 20?

The Lakers won this game authoritatively with defense, speed and Abdul-Jabbar's nonpareil intimidation. They built a significant lead and maintained it convincingly.

Nonetheless, after the lights were dimmed in the fabulous Forum and Jack Nicholson and Elliot Gould had gone home to Beverly Hills, it still was extremely difficult to know if either team could claim any appreciable edge, any real sense of superiority or advantage gained, after this excellent first act of a long coast-to-coast two-week show.