Bengt Gustafsson's greatest season ended abruptly last night when the Washington Capitals' most effective two-way player suffered a fractured tibia in his right leg just 19 seconds into the game against the New York Islanders.

By the time the 3-hour 10-minute travesty that followed had run its course, yesterday truthfully could be called one of the worst days in the 12-year history of the Washington franchise. With Mike Bossy scoring twice, the Islanders won, 4-3, and left the Capitals gasping as they headed for tonight's game against red-hot Hartford.

Washington leads Philadelphia by one point with five games remaining for each team. But without Gustafsson and Mike Gartner, who underwent knee surgery yesterday, the Capitals' chances of staying on top would appear very dim.

Gustafsson was tripped by Islanders defenseman Denis Potvin as he crossed the New York blueline and took an inside cut. Gustafsson was helped off the ice and taken for X-rays, which disclosed the break just below the knee joint.

The difficult position of the fracture means a long rehabilitation for Gustafsson. He plans to stay here until the leg heals, then return to Sweden. Whether he ever will play for Washington again is uncertain. He has indicated on several occasions before that he would prefer to play in Sweden and has an agreement to that effect with General Manager David Poile.

"I want to still play hockey, but where I play is something else," Gustafsson said. "I want it to heal and I'll stay here as long as necessary. The break is right in the joint and the knee might get stiff. If I have to, I'll work on it."

Gustafsson was left in the position of consoling those who came to offer what consolation they could.

"I'm sitting here drinking a beer and watching the game on TV," Gustafsson said. "What more can you ask? It's over now. There's nothing you can do about it, I guess. I hope the guys can get the rest of them by themselves. In one way, I was lucky. I got a new Volvo yesterday . . . and it's automatic, so I can still drive it."

Ironically, Gustafsson finished the season with 75 points, the same number as Gartner, who at least figures to be available for the playoffs starting April 9.

Gustafsson's 52 assists lead the team, he set a club record of four short-handed goals and he is a leading candidate to win the Selke Trophy as best defensive forward in the league, as well as the Capitals' MVP award.

Although Potvin's trip appeared to be both blatant and deliberate, if unpenalized, Gustafsson bore no animosity.

"I got the puck from Larry Murphy and Potvin was standing up," Gustafsson said. "All I was trying to do was put the puck on his right side and go left. He came up so fast, he put his right leg out and his leg caught my leg.

"I was moving and all my weight was on this one pointing to the splinted right leg . If I'd been spinning, I might have avoided it. It's a normal reaction to put a leg out to try to stop somebody going by and he got his leg on me."

Gustafsson was not immediately aware of the seriousness of the injury.

"I took my equipment off and I usually have bumps on both legs just below the knees ," Gustafsson said. "But it was pushed in on my right leg. The pain started leaving before I went to the X-rays. Then the pain started coming back and, when I saw the pictures, there was no question about it."

If Gustafsson was able to discuss his misfortune, others were not. Asked how Gustafsson's loss would affect the Capitals, Poile said: "I don't think I've had a chance to think about it."

Potvin expressed his regret for the injury, while having difficulty explaining his part in the incident.

"I'm deeply sorry to see an injury as severe as that. This is a game of hitting people, but I don't go out there to maim anybody. It seemed like an innocent play. I was surprised to see him on the ice. I didn't seem like a severe hit, not like I lined him up.

"I'm trying to get a piece of the man and a piece of the puck in open ice. I've been beat like that a lot of times, when the guy squeezes through. He must have planted his leg when we collided."

Referee Bob Myers not only did not call a penalty on the play, he did not whistle anything for the next five minutes, although at least 10 obvious fouls were committed by both teams.

Several players hammered Potvin into the boards, notably Kevin Hatcher and Scott Stevens. By game's end, Potvin had been charged with five penalties in separate incidents.

"Obviously, they thought I did it deliberately," Potvin said. "At least seven different guys took runs at me, which is a little out of the ordinary. But they're a team and obviously they're a tight team. They showed character coming back."

Bossy opened the scoring on a short-handed breakaway during the game's first penalty, to Islanders goalie Bill Smith for slashing Lou Franceschetti. Three seconds after the penalty expired, Hatcher tied the game.

Patrick Flatley put New York ahead to stay with 3 1/2 minutes left in the first period, which took an hour to complete.

Sixteen seconds before the intermission, there was a pileup in front of the New York net. Washington's Alan Haworth, his right wrist still sore from a recent break, became embroiled in a fight with Richard Kromm.

Smith intervened and punched Haworth. He also hit Gerard Gauthier as the linesman tried to break things up. Stevens, patiently waiting outside the faceoff circle to be sure the faceoff stayed inside the blueline, then charged Smith and threw him down. Potvin jumped on Stevens.

Smith was laughing when he rose from the ice, then was stunned to learn he had been ejected as the third man in the altercation. Kelly Hrudey relieved Smith and stopped 22 of 24 shots to win it.

"If you don't play hard, they get rid of you," Smith said. "I don't mind playing rough. I don't mind dropping my gloves. I'd rather drop my gloves than play minor league hockey."

Bossy converted another breakaway early in the second period for a 3-1 lead. It was his 53rd goal in 52 games against Washington.

Haworth's 33rd goal on a power play closed the gap, which was widened again by Brent Sutter's power-play score early in the third period. Craig Laughlin's 27th brought Washington within one with 12:39 remaining, but the Capitals could not produce the tying goal.

Beyond the scoring, there were numerous events that bordered on absurdity. Greg Adams skated into Myers in a corner, flattening the referee, and moments later was penalized for an innocuous hold on Gord Dineen.

Stevens, after being neutralized in a wrestling hammerlock by Potvin without penalty, complained to Myers and was given a misconduct penalty.

The Islanders' Bob Bourne, sent to the penalty box after taking a beating in a fight with Hatcher, became involved with a fan. Bourne stood on the bench and swung at the spectator, something he later called "stupid."

"He was challenging me as soon as I went into the box and I was sick and tired of the fans being brave on the other side of the glass," Bourne said. "It was a big act on my part. I just wanted to give him a message.

"There was a lot of abuse out there tonight. I guess the fans were just intense."

*Rangers 4, Oilers 2: In New York, Pierre Larouche scored his second goal of the game and Kelly Miller scored 31 seconds later to key a three-goal second period that carried the Rangers to the victory over Edmonton and back into fourth place in the Patrick Division playoff race.

The victory, which ended a six-game Edmonton winning streak and a personal 10-game winning streak by goaltender Grant Fuhr, lifted the Rangers one point ahead of the idle Pittsburgh Penguins in their battle for the final division playoff spot. Both teams have five regular-season games remaining, including a head-to-head meeting in New York on the final night of the season.

*Flames 6, Jets 3: In Calgary, Hakan Loob and Joel Otto each scored two goals to lead the Flames over Winnipeg.

The Flames, who scored four power-play goals, took a 2-0 lead on first-period goals 66 seconds apart while Winnipeg defenseman Mario Marois was serving a match penalty for head-butting Calgary defenseman Neil Sheehy.

*Canucks 2, Kings 1: Dave Lowry scored with 32 seconds remaining in overtime to lead Vancouver over visiting Los Angeles. Lowry took a pass from Brent Peterson just inside the Kings' blue line and drifted a low wrist shot past goaltender Roland Melanson.

The Canucks moved two points ahead of the Kings in the race for the fourth and final Smythe Division playoff spot. With five games remaining, Vancouver has 55 points. Los Angeles, with four games remaining, has 53