Of all the elements that have made the Boston Celtics the winningest team in professional basketball the past two seasons, the most praised are their depth and running game.

The Celtics have more bench strength than the Supreme Court. No team in the National Basketball Association can match the reserve power provided by Kevin McHale and Rick Robey, plus guards Gerald Henderson, Chris Ford and Danny Ainge.

"The Celtics' subs ought to enter the playoff on their own, they might finish second," Milwaukee Coach Don Nelson said after the Celtics outlasted his Bucks in a late-season game.

Boston's offensive strength always has been built around the fast break. This year, with Robert Parish and Larry Bird controlling the rebounding and Nate Archibald or Henderson handling the ball, the Eastern Conference champions got more easy baskets than any team in the league while running up a 63-19 record.

How, then, can the upstart Washington Bullets, the surprise team of the league, possibly offset these assets when the Eastern Conference semifinals resume with Games 3 and 4 Saturday and Sunday afternoons at Capital Centre?

Strangely enough, Fitch may unwittingly nullify his own strengths in an effort to adjust after the Bullets' thrilling, 103-102 upset Wednesday night in Boston.

Fitch already is showing a reluctance to utilize his bench strength. He used Robey only nine minutes, Ford six minutes and Ainge just seven ill-fated seconds in Game 2, when the rookie tried to prevent Frank Johnson from getting his game-winning shot.

"Depth is a big factor in the regular season because of all the travel and back-to-back games," Bullets General Manager Bob Ferry said yesterday. "But in the playoffs, with the games spread out, most coaches tend to play their starters more and only rely on seven or eight players."

Going just seven deep, the Bullets can match the Celtics because Jeff Ruland and Kevin Grevey have the capabilities to equal the performances of McHale and Henderson.

The Celtics' running game, their ability to break away for layups after blocked shots or turnovers, and open up 10-point leads, is Bullets Coach Gene Shue's greatest concern. However, the Bullets' offensive rebounding could force Boston to restrain its running attack.

Aside from Johnson's 28-foot, three-point shot with three seconds remaining, the Bullets' ability to rebound--particularly on the offensive boards--was the major factor in their victory. They outrebounded the Celtics, 47-36.

In the third quarter, the Bullets outscored Boston, 33-23, to overcome a 51-44 halftime deficit and take a 77-74 lead into the final period, even though they made only 13 of 32 shots. Reason: they grabbed 12 offensive rebounds and turned them into 20 points. They were missing, but retrieving their shots and putting them in.

"Our offensive rebounding was the difference," Shue said. "We weren't shooting that well, but we still caught up. It could force them to do things differently in the next game."

The only remedy for the Celtics is to keep their guards in to help box out, instead of them getting out on the break. If M.L. Carr and Archibald have to help rebound (they got only two the last game), they can't go downcourt for the long outlet pass.

"That will help us if the guards stay in," Shue said after sending his happy players through a brisk one-hour workout at Capital Centre. "To beat Boston, we have to keep them from running and make them play our game."

Shue said that Johnson did an excellent job of controlling the tempo of Game 2 and that he expects the Bullets to play even better defense in front of an enthusiastic home crowd.

Chuck Daly, who scouted the Celtics for Philadelphia, said he didn't think Boston was comfortable playing a half-court game because it was unfamiliar. The Celtics were able to outrun most teams this season, averaging 112 points per game. In three games at Capital Centre, however, they never scored 100, and Shue is hoping the trend continues.