For four games, guard Billy Ray Bates had struggled. Finally, tonight, the Washington Bullets got an encouraging sign as Bates helped them cut an 18-point deficit to three, but their fourth-quarter rally fell short and the Boston Celtics held on for a 104-97 victory.

The Bullets, who face the Indiana Pacers at Capital Centre Saturday night, are 2-3. Boston plays at Philadelphia in a matchup of unbeatens.

Bates, who had totaled 20 points in the previous games, had 15 tonight. Nine came in the final nine minutes, when the Bullets cut an 18-point Boston lead to 100-97 with eight seconds remaining. It was Bates' second three-point shot of the period that got the Bullets that close.

Greg Ballard fouled Cedric Maxwell as soon as the Celtics passed the ball inbounds, but Maxwell made both free throws. The Bullets called time and set up another three-point shot for Bates, but Robert Parish stole the ball from Jeff Ruland before he could get it to Bates.

Larry Bird made two more free throws to account for the seven-point margin.

Bird finished with 21 points and 13 rebounds and Parish had 20 points. Ballard led the Bullets with 20 points and Ruland, starting for injured Spencer Haywood at strong forward, had 16 points and 12 rebounds.

"I just wasn't executing the offense right before, and so I wasn't getting much playing time," Bates said. "I was more relaxed tonight and concentrated on doing exactly what they wanted me to do. I have to take advantage whenever I get the chance."

Bullets Coach Gene Shue has wanted to use a three-guard rotation with Frank Johnson, rookie Bryan Warrck and Bates, but said he couldn't in the past because "Billy was so inconsistent. But tonight, he was on and showed what he can do."

Bates didn't enter the game until midway through the third period. He made his first three shots, all outside jumpers, and finished six for 11 from the floor. He played the entire fourth period.

This was the usual physical Celtics-Bullets game. Center Rick Mahorn set the tone early when he leveled Bird, who was driving for a layup in the first quarter. Mahorn was booed by the capacity Boston Garden crowd of 15,320 the rest of the night, but the Bullets never folded. Mahorn and Parish almost came to blows in the fourth period, but were separated by officials and teammates. Shue and Boston Coach Bill Fitch also ran onto the floor to keep order.

The Celtics appeared to have the game in control when a dunk by Rick Robey, after a 20-foot blind pass through traffic from Bird, gave them a 92-74 lead with eight minutes remaining.

But the Bullets, who lost all six regular-season games to the Celtics last year and then lost to them in the Eastern Conference semifinals, 4 games to 1, kept coming back. With Johnson penetrating and Bates scoring from outside, they crept back in the game.

A fast-break basket by Johnson and Bates' first three-pointer cut the lead to 97-91 with 2:54 remaining. That's when Fitch, who had been using his second unit most of the period, quickly reinserted Bird, Parish and Tiny Archibald. Archibald made a 17-footer and after a free throw by Bates, Boston led, 99-92, with 15 seconds remaining.

Ballard made two free throws after being fouled by Maxwell, and the Bullets fouled Maxwell as soon as the Celtics passed inbounds. He made one of two free throws for a 100-94 lead with 12 seconds left.

"We kept giving ourselves a slight chance to catch up," said Shue. "Sometimes it'll happen that they'll miss their free throws. If they had tonight, we might have pulled it out."

Johnson had a career-high 15 assists and four steals, but made only three of 15 shots from the field. The other starting guard, Warrick, missed his only shot in 27 minutes.

The Bullets put themselves in deep trouble in the first half. Mahorn opened the second period with two baskets to cut the Celtics' lead to 26-22, but Boston scored 14 of the next 18 points to go ahead, 40-26, with 7:32 left in the half. Bird had six of those points.

Most of the damage in the quarter was done by reserves Kevin McHale and Quinn Buckner, who combined for 21 of Boston's 33 second-quarter points as it took a a 59-43 halftime lead.

McHale dominated play inside with 10 points and Buckner, not known for his outside shot, made four straight jumpers and had 11 points.

"We weren't playing as aggressively defensively as we needed to early," said Ballard. "And we were breaking our plays. That enabled them to get a lot of steals and put us out of synch. We did better in the second half, but we were so far behind . . . "

Said Shue: "We're a team that really has to execute our plays precisely. The Celtics forced us into several mistakes and we allowed them too many shots in transition. In the secxond half, we did much better in forcing them into a half-court game, which is the only way we can play them."