If the Washington Capitals beat the Minnesota North Stars this season, it will have to be in the Stanley Cup playoffs. Such a matchup would not be displeasing to Minnesota Coach Glen Sonmor, who sported a broad smile after the North Stars earned a 2-1 victory last night at Capital Centre.

"I hope we'll see them in the playoffs," Sonmor said. "That will mean we're both doing well."

It also would probably mean that the North Stars would advance to the second round. Washington has not beaten Minnesota since March 4, 1979. For the second straight year, regular-season play between the teams ended with three Minnesota victories and one tie.

In the four games this season, the Capitals have collected only five goals against Minnisota netminder Gilles Meloche. They were outshot last night by 248--18 and Meloche did not need his usual heroics to shut down Washington.

It is apparent that the North Stars, who have beaten Washington three times in less then three weeks, have devised a game plan that is successfully shackling the Capital offense. Much of it involves extra concentration on Washington scoring threats Mike Gartner and Dennis Maruk. c

Gartner managed three harmless shots last night, while Maruk did not get one. The Capitals' fourth line, composed of three centers, produced the lone goal, Wes Jarvis firing a 30-footer down the middle while the double-shifting Maruk distracted Meloche in the crease. Glen Currie was the other forward on the ice.

Jarvis' ninth goal of the season sent the Capitals ahead at 3:09 of the second period. A bit more than five minutes later, the scoring for the game was complete.

Tim Young put a 40-footer past goalie Dave Parro at 6:06 as Al MacAdam adroitly screened Washington's rookie goalie. It came on a power play, with Jim McTaggart in the box. McTaggart fought Tom McCarthy and, for the third time in four games, drew an unsportsmanlike conduct minor in addition to the usual fighting major. It is obvious that McTaggart must drop the helmet-yanking routine from his ring repertoire, since the resultant hair-pulling is a definite no-no.

MacAdam scored the winner at 8:15, converting the rebound of a shot by Bobby Smith. The pair got loose on a two-on-one break when MacAdam beat defenseman Rich Green to Steve Payne's carom pass off the right-wing boards.

More than half the game remained, but neither team would score again, although both struck posts late in the second period.

Minnesota shut down the Capitals in the final 20 minutes and it was not until 12 seconds remained that Washington was able to get enough skating room to lift Parro for a sixth skater. That proved futile, since it came on a faceoff just outside the Minnesota blueline and on the draw the puck slid all the way to the Washington goal line.

Although Minnesota is a hot team, having lost only twice in its last 15 games, there was considerable dissatisfaction with the Capitals' performance among the crowd of 9,394. Much of it, as usual, was spurred by the failure of the Washington power play, which batted 0 for 4 and has been successful only twice in the last 59 opportunities.

In practice Tuesday, the Capitals had difficulty scoring against Parro despite the absence of any other defenders. So it was no surprise that the North Stars' excellent penalty killers had no trouble maintaining the status quo.

"It's finishing off," said Coach Gary Green, who used everyone but McTaggart and Allen Hangsleben in extra-man situations. "When we got good scoring chances, you could almost see the sawdust falling off their sticks from grinding too hard. It's a matter of too much effort rather than not enough."

Of suggestions that he move Bengt Gustafsson back onto the Ryan Walter-Gartner line to keep the opposition from keying on Gartner, Green said, "I don't think you could consider taking Gusty off the line with Rolf (Edberg) and Vervy (Dennis Ververgaert). They've had so many opportunities lately. They outplayed the (Mike) Eaves line and I thought they would win it for us."

On the reason for the low-scoring contests that have abounded in the series, Sonmor said, "We're both very strong defensively and we both check very well. The game often turns into this kind of game. And there has been excellent goaltending almost every game. Your kid (Parro) has been great the last two games and Meloche is positively brilliant against this team."

"I think we're more physical and aggressive than they are," Green said. "But as far as quickness and finishing off ability, they take the cup."

Or at least the series against Washington.