Perhaps the most remarkable aspect of the Washington Bullets' domination of their playoffs series with San Antonio is that they've won despite an unnerving slump by one of their key players, Mitch Kupchak.

Kupchak has yet to play one of his typical, reckless games against the Spurs, yet Washignton still can wrap up the best-of-seven series tonight with a victory here (8:30, WDCA-TV-20).

"I keep thinking where we will be if Mitch catches fire," said Bullet Coach Dick Motta, whose team holds a 3-1 advantage in games. "It's pretty impressive that we've done this much without him."

Motta readily admits that if someone had told him Kupchak would average only eight points and shoot just 37 percent (compared to 15.9 points and 51 percent in the regular season) through the first four games, he would not have liked his club's chances.

"Mitch had to be one of the important players going into this series," said Motta. "With him, we have so much front-court flexibility, especially at center. He gives San Antonio a lot of matchup problems."

However, the Bullets, who entered the series as decisive underdogs, have wound up controlling things so much that the Spurs abandoned their usual run-and-gun tactics in game three Sunday for a hesitant, pattern offense.

The Bullets think the Spurs are running scared and, in the process, are becoming confused. They hope the result will be a fourth straight victory tonight and an end to the series.

A good performance from Kupchak would improve Washington's odds. So far the Bullets have been getting a superior effort at center from 10-year veteran Wes Unseld, but Motta would pefer to use Unseld less than the 41 minutes he playes Sunday, while increasing Kupchak's time to more than the 15 minutes he put in that game.

"I feel good and we are winning, and that's really all that matters," said Kupchak, who has scored only 15 points, and just one Sunday, the last three contests. "If we were losing and I was in a slump, 'I'd be down about it, 'cause I'd feel I was the reason.

"I think about how I'm playing, but I'm not upset about it. I'm just not scoring well. But Bobby (Dandridge) and Elvin (Hayes) are doing so well, I don't have to score as much."

Kupchak said he is just as aggressive and as intense as ever, and that he has not toned down his play since getting into a fight with the New York Knicks' Lonnie Shelton in a game March 30. Both were elected and later fined $1,500 by NBA Commissioenr Lawrence O'Briwn.

"The fight doesn't bother me," Kupchak said with some hestitation. "That's behind me, I've got to think about the future."

Kupchak was upset at the time because, although he plays aggressively, he is not a fighter and didn't think he had done anything to provoke Shelton.

In the regular-season games after the scuffle, he gave no evidence his style had been affected. He was probably the most efficient Bullet during the streak when the team played poorly.

But the playoffs have been another story.He scored 15 points in the second game against Atlanta, and 18 in the opener against San Antonio, both times starting for Dandridge. But he seemed nervous and overanxious even in those contests, and Motta now fears he is trying too hard.

"When Mitch isn't playing well, he will push himself, almost as a punishment," said the coach. "He's really rough on himself and he shouldn't be."

Entering the quarterfinals, Motta figured he would be able to use Kupchak to stop any attempts San Antonio might make to lay off Unself and double-team Hayes. Motta would rush in Kupchak and force San Antonio to play a more honest defense.

But even without Kupchak scoring, the Spurs have been burned double-teaming. Both Hayes and Dandridge have been passing to open teammates instead of forcing shots and Dandridge, especially, has been finding Unseld free under the basket for open layups.

"(Billy) Paultz is turning his back on me," said Unseld "more than he is really double-teaming. I'm just going to the basket and Dandridge is doing a great job of finding me.

"That's the difference between now and when people have left me before. Dandridge is looking for me. But I'm sure San Antonio will adjust."

Kupchak doesn't think so.

"If you leave only one guy on Elvin, it's almost an automatic two points," he said. "We have to make a good pass to get the ball to Wes or me. I think they'd rather take a chance on that pass."

Unseld has been getting so many layups that his playoff average has risen to 13.2, five points more than in the regular season. He is shooting 63 percent (compared to 42 percent before) and is tied with Tom Henderson fort he team lead in assists with 20.

Eight of those assists came in game three, mostly off passes from the high post, so in game four Paultz was more aggressive and tried to deny Unseld the ball up high. But that allowed Unseld to roll more easily tothe basket, and prevented as much double-teaming by the Spurs underneath.

In what may be the last playoff of his career, Unseld also has emerged as a major factor in the Bullets' surprisingly consistent running game.

"In Elvin and Wes, we have two great rebounders who can get the break going," said Motta. "We are one of the new teams who have been blessed that way and now we are taking advantage of it. We should be able to run with them in the lineup."