The Washington Capitals marked the end of their fourth season last night by attending a fan club-sponsored banquet at the Bolling Air Force Base Officers' Club. Nobody was certain there was anything to celebrate.

The Capitals closed with convincing victories over Buffalo, Pittsburgh and Atlanta, after tying Boston and Montreal. There was no better team during the last two weeks than Washington. Conversely, there was no worse team during the other 24 weeks.

A year ago, the Capitals won a club-record four in a row before finishing with two losses to Montreal. There was reason to believe that success would carry over and provide the impetus to a Stanley Cup playoff berth.

So what happened? The Capitals won their fourth game on Dec. 11, their 28th of the season.From Oct. 26 to Dec. 7, the Capitals went 20 games without a victory. The pressure of that winless streak destroyed the season for some players, who skated in fear of committing the error that would lose another game.

Injuries piled up in incredible fashion, with management calculating that 283 player-games were lost by season's end, not even counting the absence of Pete Scamurra. Only two players, Guy Charron and Gord Smith, participated in the full 80-game schedule and Charron was less than 100 percent for much of the first half of the season.

Ace Bailey, Ron Lalonde, Bill Riley, Tom Rowe, Bob Sirois, Rick Green, Yvon Labre and Jack Lynch were missing for sizable periods, several just when they seemed to be fitting into productive roles.

Labre, who underwent knee surgery Nov. 8, was probably the key absentee. If a team is down, there is no better tonic than to have its captain racing around the ice banging into people, giving 100 per cent every second no matter the score. When Labre achieved maximum physical fitness, the Capitals began to roll.

Besides the injuries, there were notable individual failures. Walt McKechnie never fit in with the "hard work" ethic and was traded, after some disruptive incidents that included exile with pay. Gary Smith, supposed to fill Ron Low's pads, couldn't stop a puck. A lot of wingers couldn't score.

Over the season, the Capitals collected 14 fewed points than last year, scored 26 fewer goals and allowed 14 more. They achieved a pitiful 12 per cent success on the power play, permitting opponents to convert 28 per cent.

Worst statistic of all was the yielding of 15 shorthanded goals.

For all the disappointment, there were also bright spots, Robert Picard, from a bewildered rookie, developed with partner Bryan Watson's help into a confident, puck carrying defenseman. Rowe, close to minor-league status on several occasions, stopped pressing and started scoring with goals in five of the last six games.

Rick Green had some horrid moments, but when he was good, he was, in rhyme without reason fashion, very, very good. Mike Marson suddenly, late in the year, showed signs that his lengthy learning process had borne fruit. Little Rick Bragnalo, consigned to Hershey early, returned to provide his unmatched hustle. Charron and Sirois confirmed that they are bona fide major league talents.

Jim Bedard, called up from Hershey in the team's darkest hour, displayed an exciting, successful brand of new-image goaltending, skating into the faceoff circles to cut down angles and enemy shots. He became a third defenseman for a team that needed all the defense it could muster.

Best of all, the Capitals not only refrained from dealing away draft choices, but acquired a couple. Cleveland gave up its No. 2 this year in the McKechnie deal : Pittsburgh passed on its No. 1 in 1979 for Hartland Monahan.

The late surge cost the Capitals first pick in the June draft, meaning Ottawa's coveted 6-4 center, Boh Smith, is probably headed either for Minnesota or a team that will provide the North Stars with a talented defenseman. But the No. 2 man, either Ryan Walter of Seattle or Bill Derlago of Brandon, should be an asset to the Capitals next season. Also there are Eddy Godin and Mark Lofthouse, anxious to leave the farm.

The big question remains unanswered. Are the current Capitals as talented as they seemed in the closing segment of the season? Two weeks ago, it appeared likely that General Manager Max McNab would have to make wholesale changes befor enext season. Now, he may be tempted to go slow, in the belief, real or misguided, that the present roster will carry its success into another campaign.

Regardless of the prospects for next year, and the apparent anxiety of the Capitals tm begin the new season, there must be considerable agonizing this summer over what might have been.

"The hell with next year," said Coach Tom McVie. "We could have won alot of hockey games this year playing the way we did the last two weeks. This is exactly what we expected to come out of training camp with. I don't know why didn't, and I don't know why things suddenly turned around."1p He and his players figure to do a lot of tossing and turning looking for those answers. They will be doing considerable tossing and turning in preparation for the new season, too. As usual, there will be summer-long programs for each man, to guarantee his appearance at training camp in peak condition.

"I'm not going to change," McVie said. "We're going to work hard and be as strong as anybody in the league. I don't plan to do anything different." Not even on the power play?

Charron, Picard Invited

Center Guy Charron and defenseman Robert Picard of the Washington Capitals have accepted tentative invitations to represent Canada in the World Ice Hockey Championships at Prague, April 26-May 14.

The final roster will be determined Sunday, after the preliminary round of the Stanley Cup playoffs. Players participating in the Stanley Cup quarterfinals are not eligible.