The Washington Capitals returned to sweet 16 status last night after slipping a rung in the playoffs sweepstakes. By dumping the St. Louis Blues, 4-2, the Capitals moved two points ahead of both Detroit and Vancouver in the struggle for that final Stanley Cup berth.

Tuesday, Washington had fallen to 17th, and that flirtation with obscurity provided a necessary spur in last night's rematch with a team that had overwhelmed the Capitals Saturday in St. Louis, 6-2.

"We got fired up, because we knew we wanted to be 16th and not 17th," said Paul Mulvey, whose 13th goal sent the Capitals ahead to stay. "Let those other teams fight for 17th, we don't want it."

"Everybody is so determined to make the playoffs, there was no way we were going to lose tonight. We've worked too hard to quit now. We had a little time to think about it, and running for planes and buses, and we were a little more relaxed. The whole atmosphere playing at home is so much better."

An enthusiastic crowd of 16,156, unheard of for a midweek hockey game here, contributed to that winning atmosphere. After a few boos were heard early during a power play that never got organized, it was all sweetness, light and adulation.

Bengt Gustafsson started the scoring with his 20th goal, on a setup from Rolf Edberg, his fellow Swede who eventually closed the Washington parade with his 21st. Edberg had scored No. 20 in Monday's loss at Toronto.

"We're having a race," Gustafsson said. "He get 20 and I get 20. Now he get 21, I have to get 21."

"There are only five games left, we can't stop now," said Edberg, named the game's No. 1 star for an outstanding all-round performace.

A proud spectator was Arne Stromberg, the Capitals' European scout, who brought Edberg and Leif Svensson to Washington and urged the capitals to try everything up to and including kidnapping to tear Gustafsson away from Edmonton.

Mulvey balsted a 45-footer past St. Louis goalie Mike Liut, who made 15 second-period saves to keep the Blues in the game, and the Capitals carried a 2-1 lead into the final period.

Mike Gartner's 35th goal, on a blast from the slot after the puck skidded off Ryan Walter's stick, gave Washington some breathing space. Then Edberg rebounded a Robert Picard shot to put it away.

Both St. Louis goals, by Bernie Federko and Perry Turnbull, came on power plays. Except for penalty situtations, the Capitals were in control. But the Blues' excellent penalty killers, among them former Cap Hartland Monahan, blunted the Washington extra-man attack, and St. Louis took advantage of some foolish penalties to swarm around goalie Wayne Stephenson.

In each period, Washington came out buzzing, although the Blues were able to reverse the momentum with the aid of those ill-advised violations.

Washington had a 1-0 lead and a 9-1 edge in shots when Pat Ribble was thumbed for elbowing Larry Patey in the first period. Federko wasted two Turnbull setups on that opportunity, then connected while Walter was off for hooking.

After eight minutes of the second period, the Capitals had regained the lead at 2-1 and were ahead in shots, 7-0. Then the shorthanded Blues acquired renewed life while Ralph Klassen was serving a holding penalty.

It took the Blues eight minutes to record a shot in the third period, too, and they never were fully able to get untracked that time, although rookie Turnbull connected with Bob Sirois in the box for tripping.

Stephenson made 25 saves in posting his 17th victory of the season, a Capital record. It came on a night when Washington was reaching 63 points for the second straight season. It has never gone higher.

"Everybody played a strong game when we had to," Stephenson said. "This should give us a little confidence again for the big games coming up next. It was a tough weekend all the way around and we just can't skid too long. We didn't play well on the road and everbody felt the pressure and had to bounce back."

For a change, the Capitals won on both the scoreboard and the fight card. Alan Hangsleben, slashed in the left leg by the Blues' Neil Komadoski, pounded his tormentor to the ice while everyone else was at the opposite end. It was sweet revenge for Hangsleben, who was blasted by the Blues' Wayne Babych in St. Louis Saturday.

"I swung first in St. Louis, lost my balance, and never got it back," Hangsleben said. "When you miss once, you have to take three punches to get your balance back. I like to let the other guy swing first."

Komadoski swung, missed and wound up nodding his head in acknowledgement of defeat. It is nice to win a fight, or make a big play, or even score a 20th goal. But the score is paramount.