It took nine years, but the Washington Capitals finally have qualified for the Stanley Cup playoffs.

Alan Haworth scored three goals tonight against former Buffalo teammate Don Edwards to carry the Capitals to a 4-2 victory over the Calgary Flames and assure first-ever postseason competition at Capital Centre.

Goaltender Pat Riggin stopped 26 shots to deal his former Calgary teammates their first home-ice loss in 11 games and extend his own unbeaten streak to eight games.

Each team scored once in the first period, with Haworth getting his 16th goal for Washington and defenseman Phil Russell his 11th for Calgary.

Haworth's 55-foot shot down the middle at 8:55 beat Edwards low on the stick side as Bob Carpenter skated in front to distract the goaltender.

Dave Hindmarch set up Russell's score, carrying the puck down the left side and dropping it back to Russell, who hit the far corner from the left-wing circle at 12:53.

The Capitals survived two difficult penalty situations. Riggin, making his first appearance here since the Flames dealt him away, was fortunate when both Lanny McDonald and Kent Nilsson shot wide from close range while Calgary held a four-on-three advantage. That came about when Randy Holt intervened in Bobby Gould's high sticking quarrell with Carl Mokosak and was assessed an extra minor for roughing Mokosak.

Late in the period, with eight seconds left on a tripping minor to Haworth, the Capitals were placed two men short when referee Ron Hoggarth called a bench minor penalty on Coach Bryan Murray. Riggin made an outstanding stop on Doug Risebrough during the brief five-on-three segment.

Murray had complained because Hoggarth and the two linesmen failed to rule a deliberate offside on the Flames' Paul Reinhart, who spun and shot the puck offside to avoid a breakaway by Washington's Glen Currie. At period's end, Murray accompanied the three officials to their dressing room, arguing all the way.

Edwards made big saves on Gould and Ken Houston, both former Flames, and was fortunate when Carpenter's rebound of Haworth's shot struck a post.

Washington outshot the home club, 14-4, in the second period and took a 3-2 lead on power-play goals by Haworth and Timo Blomqvist. Jamie Macoun scored for Calgary.

Macoun was off for hooking Ted Bulley when Haworth posted his second goal of the game, at 4:04. Haworth backed away from Reinhart, whose stick had come within inches of his head, then blasted away from the left-wing circle.

Macoun, an Ohio State product who recently joined the Flames, scored his first NHL goal at 12:45, hitting the far corner from the right-wing circle after the Capitals were unable to clear their zone.

Washington regained the lead 51 seconds later, on Blomqvist's first goal this season, a slap shot from the right point that struck Reinhart's skate and deflected behind Edwards. Russell was the man in the box, for slashing Currie on his bare left hand after Currie had dropped his glove.

The Capitals had ample opportunity for further scoring. Edwards made some outstanding saves on Bulley, Houston and Holt, while Gaetan Duchesne was just wide off a setup by Currie. At the other end, Jim Jackson rattled a post.

Early in the third period, Riggin made a superb stop on Guy Chouinard's deflection of a drive by Kari Eloranta. When play moved to the other end, Haworth completed his hat trick by pouncing on the puck at the left-wing boards and carrying it across to the slot before lining a 30-footer past Edwards at 3:12.

Riggin stopped Jim Peplinski twice while each team was a man short, then Peplinski's third try went wide. With Washington on a power play, Nilsson picked off Bengt Gustafsson's pass, but Riggin moved out smartly to foil the breakaway.