Defenseman Brad Marsh, Philadelphia's acting team captain, was the uncontested No. 1 star of the Flyers' pivotal 4-2 NHL playoff victory over the Quebec Nordiques Thursday night.

If stars were awarded for forthrightness, Marsh also would be an overwhelming winner, especially because he plays on a team where secrecy is a way of life.

The Flyers have taken a 2-1 lead in the best-of-seven Prince of Wales Conference championship largely by hitting anything wearing a fleur-de-lis that tries to move. The principal targets have been the Nordiques' chief scoring threats, Michel Goulet and Peter Stastny.

"We're not singling out anybody or playing one man against another," Coach Mike Keenan said. "We're playing five-man defensive units."

During Thursday's game, while he and Goulet were skating up the ice behind the play, Marsh suddenly slashed Goulet in the legs. Goulet turned and slashed him back. Linesman John D'Amico reported the incident to referee Bryan Lewis, who assessed both players major penalties. That put the Flyers in a tough spot for five minutes, since they had been reduced to four defensemen by Brad McCrimmon's shoulder separation that required surgery this afternoon.

Acknowledging that it was a "stupid penalty" under the circumstances, Marsh said of his two-hander, "I didn't think the ref was looking, but the linesman saw me. Luckily, he (Goulet) slashed me back. Sometimes in the course of a game you lose your composure and get stupid penalties."

If Marsh occasionally makes "stupid" moves on the ice, they never will match the foolishness of the Calgary Flames, who dealt him to the Flyers in 1981 for journeyman Mel Bridgman. Where he was scorned in Calgary for his failure to try to run opponents through the boards, Marsh is revered in Philadelphia for his willingness to dive in front of opposing shots and to wrestle players out of the path of goaltender Pelle Lindbergh.

"He's played exceptionally well all year and this was just another example of his outstanding defensive play and outstanding leadership," Keenan said of Marsh's play on Thursday. "He has driven the level of his play up to the level you saw tonight. If anyone came near in a blue sweater, he was willing to take the man and complete his check."

If completing the check often resembled a calf-roping contest at the Calgary Stampede, it was a frequent reminder that Marsh will do anything to keep the puck away from the Flyers' net.

Marsh has had a checkered career, to say the least. Drafted in the first round by Atlanta in 1978, he joined the Flames that fall and played 257 straight games, before being dealt to Philadelphia.

Because of the vagaries of the schedule in 1981-82, he played 83 regular-season games, an NHL record. He was captain of the Flames before the trade and has been around so long that it surprised some people when he celebrated his 27th birthday on March 31.

The big rap against Marsh is a lack of speed and he has been known as "Snowshoes" for much of his NHL career. Bob Clarke, the Flyers' general manager, noted that "Brad's problem is that his feet are as big as his heart."

Although Marsh is his own most severe critic, he does not feel that speed is essential.

"I think it's more important to be in the right place," Marsh said. "I know how to position myself and I know what I can't do. I know I'm not like Mark (Howe). He can make a mistake and get back in the play with his skating. If I make a mistake, I'm dead.

"But I don't think I'm really slow. I guess I look big and clumsy (6 feet 3, 220 pounds) and since the guy I'm playing with is usually a smoother skater, I look a bit of an oaf out there. I'm always very hard on myself and I know when I've played bad. I think I'm playing well right now and I've had a good season. I'm more concerned with my opinion than the media's opinion."

Besides diving in front of an inordinate number of shots Thursday, Marsh reached out with his glove while lying on the ice to rob Brad Maxwell in the third period with the Flyers ahead, 3-2. Typically, he downplayed it.

"Things are going well for the Flyers now and it hit me," Marsh said. "Some other night it might have gone over my glove and gone in front. I didn't think about it. You don't have time to think out there. Sometimes you're a hero; sometimes you get beat."

Flyers right wing Tim Kerr flew to Los Angeles today to be fitted for a special brace on his injured right knee . . . Keenan said it was "not out of the question" for Kerr and Dave Poulin (left knee) to play in Sunday's fourth game here.