After all the theories are analyzed and after all the excuses are offered, the fate of the Washington Bullets always seems to hang on one overriding factor: the performance of Elvin Hayes.

It is a burden Hayes has tried to live with since coming to Washington six years ago. He believes it is unfair to him and his teammates. And, despite an improved ability lately to shake off criticism, he still broods over his occasional poor efforts, particularly in the playoffs.

Hayes had hoped that his outstanding play last season during the Bullets' march to the NBA title would finally free him of the pointing fingers and veiled snickers.

But he was wrong. His 10-point production against Atlanta Tuesday night in the second game of the Eastern Conference semifinal series has turned this into a very long week for him. He believes fans already have forgotten how he overcame some so-so outings a year ago to wind up as the Bullets' leading scorer during the playoffs. He declined comment yesterday.

When Hayes plays well, Washington does not necessarily always win. But when he is below his usual level of quality, the team almost always loses. That is how valuable he is to the franchise.

And that is why the Bullets need at least one sensational game from Hayes this weekend in Atlanta for them to regain the edge in the series. If Washington can win either tonight (7:308 WDCA-TV-20) or Sunday in the Omni, where the Hawks have won 17 straight, the damage caused by the Tuesday night disaster will be wiped out.

"Elvin didn't play any worse than everyone except Bobby (Dandridge) and probably Larry (Wright)," Coach Dick Motta said. "It would be unfair to give him too much of the blame for what happened to us Tuesday.

"But even though I think we are a team, not a one-man show, there is no question Elvin is very, very important to us. That's why our offense is geared to getting it into him. We need him to score or to pass to someone who is open."

When he first came to the Bullets, Hayes might not have wanted such a heavy responsibility placed on his shoulders. But in the past season or more, he has shown an increasing ability to react to unfavorable comments with highly favorable performances. That was never more apparent than in last year's playoff series against Philadelphia when he would not bend in the face of George McGinnis' verbal pressure.

Against the Hawks, he does not have to overcome a McGinnis or any player near that stature. Instead he apparently will be guarded a great deal the rest of the series by two players Motta calls "workhorses": Steve Hawes and Tom McMillen.

Neither is particularly quick nor talented, but both are convinced the one way to stop Hayes is to front him, refusing to let him receive any easy passes.

So they are intent on scrambling and lunging until he gets discouraged and stops working to get open. Once that happens, they feel he will be eliminated from Washington's offense.

"Fronting Elvin is nothing new," Motta said. "He's had every conceivable defense tossed at him that you can think of , especially since Golden State beat us in 1975 by double-teaming him with a guard.

"We have counters to anything they want to do. We just didn't execute them worth anything the other night. It's as simple as that. You can't shut off Elvin, not when he is in his game and we are moving the ball correctly.

"You watch. The guy who is assigned to Tommy Henderson will wind up guarding Elvin 80 percent of the time. It's just the way the league feels he can be stopped and it's up to us to handle it like we did the whole year."

Another Hawk forward, Dan Roundfield, probably will start off on Hayes while John Drew again tries to handle the elusive Dandridge. But if games three and four follow the same pattern as the opening two, Drew will get into early foul trouble or be unable to cope with Dandridge's moves.

In either case, Hawk Coach Hubie Brown then would move the bigger (6-8) Roundfield over to Dandridge and bring in McMillen to take on Hayes. There also is the possibility that Hawes, the starting center, will cover Hayes early while Drew is assigned to Wes Unseld, who has been very effective at the end of the season against smaller forwards.

"I know Atlanta has been saying a lot of things about how their changing defenses and all that beat us," Motta said. "We know how they feel. We went through it last year. You feel like you are on a joy ride and everything you say and do will come out right.

"They'd be crazy not to try to do something on Elvin. He is going to start every game by running to his favorite spot to the left of the basket and if you let him have it there, we are going to beat you easy.

"If the other night and even the first game was the best they can do, then we will win the series. If we don't, it will be our own fault. They haven't played all that well, but we have been lousy. Period."

There is no reason for Motta and the players to expect another below-average game from Hayes. He was a tower of strength over the final third of the season, helping to carry the club (along with Dandridge) while many teammates were hindered by injuries. Every time he appeared to be weary, he responded with one of his characteristic 30-point, 15-rebound efforts.

He would benefit in this series from a faster tempo, but for the Bullets to run, he and Unseld must do a better job on the boards. Washington, the league's No. 1 rebounding club, has pulled down just 12 more missed shots than the Hawks, who have just as many offensive rebounds (29) as their opponents.

"Atlanta is a team of role players," Motta said. "That is how they manage to use nine guys successfully. But they also play by rote. Hubie tells them what to do at every step.

"We were able to take Philly and San Antonio and Seattle out of their offense and game plan last year, but we haven't done that to the Hawks yet, although because they are so mechanical, they should be the easiest in the league to beat that way.

"This series so far reminds me of our first West Coast trip this year when we lost all four games. We just felt that if we showed up, we'd win. Well, we learned our lesson from that and I think the first two games here have taught us another lesson.

"Just don't cancel your plane reservations for the rest of the series. You might need them."

Yesterday, in what might have been the most physical practice of the season, there were a couple of near fights. Unseld and Mitch Kupchak exchanged words and shoves before Hayes stepped in between . . . "If we play like that against Atlanta, I'd hate to be the Hawks," Motta said . . . Unseld said he can't remember the last time the Bullets played well in a game. "We are due, but first we have to forget about anything that is bothering us and just concentrate on this series." CAPTION: Picture, Elvin Hayes