For the sixth time in their seven years, the Washington Capitals played a game without a penalty last night. That was part of the game plan, to keep the potent Quebec power play off the ice. The rest of the game plan was admirably fulfilled, too, and afterward Coach Gary Green could truthfully say, "Our guys put on one hell of an effort. We skated and worked as well as we have in any game all year."

Outshooting Quebec by 38-22, the Capitals deserved to win this contest, so vital to their playoff chances. They didn't. The one team absolutely essential to any hockey team's success, keeping the puck out of its net, was the one slipshod area. As a result, the Nordiques skated away 6-4 winners.

Mike Palmateer was beaten on five of the 14 shots he faced and Dave Parro yielded a goal on a shot from the blueline that gave Quebec's Robbie Ftorek his first National Hockey League hat trick. The result left many of the 8,520 watching in an angry state and several stayed to heckle and hurl junk while Ron Weber attempted a postgame interview with the Nordiques' Jacques Richard.

The worst news for Washington came even later. The New York Rangers upset Boston and Toronto upset St. Louis and Edmonton upset Minnesota. Suddenly, the Capitals were 17th and out of playoff territory, trailing Edmonton by one point, Toronto by two and the Rangers and Pittsburgh by four.

Twelfth-place Quebec, playing its fourth game in five nights, was finishing that difficult stretch unbeaten and, with 69 points, was reaching champagne-buying time in its pursuit of a playoff berth.

"We're not in the playoffs, but we're close, that's for sure," said Quebec Coach Michel Bergeron, who was receiving congratulations from his players for reaching a personal .500 record since taking over from General Manager Maurice Filion two weeks into the season.

Bergeron, too, was generous in praise of the Capitals' effort, saying, "Washington played a good game. They were forechecking us all game. We were really tired, but we've got sharp shooters and (goalie Daniel) Bouchard gives everybody confidence, making the key saves."

The saves that were not made at the other end were even more imporant. The Nordiques grabbed a 2-0 lead, but Bob Kelly cut it in half with the first of his two goals 31 seconds before the first intermission. Instead of the Capitals seizing momentum, however, they fell behind, 3-1, early in the second period when Palmateer blew an unscreened 60-footer by Dale Hunter.

When goals by Kelly and Rolf Edberg gave Washington a 3-3 tie, it took Quebec only 62 seconds to regain a two-goal margin. Richard flipped the puck past Palmateer's glove after slipping behind Howard Walker and Ftorek, on a breakaway, faked Palmateer down and lifted the puck over him.

That was all for Palmateer, Green summoning Parro to the rescue. He made several good stops and there still was hope of victory when Mike Gartner netted his 40th goal at 6:35 of the third period to make the score 5-4. But Ftorek's 60-footer sailed past Parro's glove and spectators started heading out the exits.

Washington pulled Parro for a sixth forward in the last minute, but Ryan Walter shot wide and Gartner dribbled the puck off a post, and the Nordiques were pounding each other on the back.

Asked whether he was surprised to have gotten a hat trick, Ftorek said, "I'm always surprised when my goals go in. I'm very happy about that one (his last), not because it was my third, but because Washington had just closed within one and was pressing us."

While losing the four-game series to Quebec, the Capitals scored 17 goals. That would be enough to sweep some series, but in this case the Nordiques scored 30. Oddly, the Stastny brothers, who had seven goals and eight assists in an 11-7 victory here Feb. 22, did not earn a point last night.

Gartner tied a Washington club record by scoring a point for the 10th straight game and Walter matched another by posting an assist for the eighth game in a row. Edberg deserved credit, too, for playing well in his first action since his jaw was broken in Calgary Feb. 5.

"I'm afraid to jump on the scales, maybe I'd lose my confidence," said Edberg, who has lost considerable weight after four weeks on a liquid diet and one week of tiny pieces of spaghetti. "I'll be glad to get this rubber band off my teeth so I can eat something. But what I really wish is we could have got at least a point out of this game tonight."

The Capitals' home record dipped to .500 with this defeat, 15-15-5, and no congratulations were being handed out for that penalty-free game. In fact, Ftorek raised a question on the subject.

"I don't know too many teams that would come out and play a game like that, of this importance, and don't get a penalty," he said.