Philadelphia's smooth-skating center, Rick MaCleish, tallied the game's first goal on a rare penalty shot to ignite the Flyers to a 4-2 NHL victory over the New York Islanders Monday night, keeping the Flyers' first-place hopes alive.

"Yes, I was nervous; anybody would be nervous at a time like that," MacLeish said about his wrist shot that beat New York goalie Billy Smith in front of 17,000 screaming fans in Philadelphia's Spectrum.

"Sure, there's a lot of pressure on you, but you just have to concentrate," said MacLeish. "If you got your mind on what you're going to do and go ahead and do it, you'll be all right."

The penalty shot was awarded at 6:20 of the opening period after referee Bob Myers ruled that New York's Jude Drouin had fallen on the puck in his own crease. The puck was placed at center ice and MacLeish took it and skated in on Smith.

"You look at the replay and see how little room he had to shoot," the fiery Smith said afterward. "He came in, made a good move and picked the corner unbelievably. It was a good shot. You have to give him credit."

MacLeish goal marked the first time this year Philadelphia has scored the first goal on the Islanders and the Flyers never let up in beating New York for the first time in five games this season.

Mel Bridgman and Bill Barber followed with goals to make it 3-0 before New York's Bob Nystrom cut it to 3-1 late in the second period. Reggie Leach's power-play goal in the final period broke the game open for the flyers before New York defensemen Denis Potvin tallied the game's final goal.

In the only other game in the National Hockey League:

Canadiens 5, Canucks 1

Steve Shutt fired in a pair of goals to reach the 200-goal plateau for his career and Guy Lafleur notched his 300th career goal in Montreal's easy win over the Canucks. Yvon Lambert and Pierre Larouche also tallied for the Canadiens while Vancouver's Mike Walton spoined Ken Dryden's shutout bid with a third-period goal.

There were no games in the World Hockey Association, but the Winnipeg Jets made new, anyway.

Winnipeg's Ulf Nilsson and Anders Hedberg - the second - and fourth-leading scorer in the WHA, respectively - have signed two-year contracts with the New York Rangers of the NHL, effective with the 1978-79 season. The players will each receive a reported $600,000 per season - making the high-scoring Swedish forwards the highest-paid active players in the NHL.