In Philadelphia, they called Ken Linseman the "Million-Dollar Mistake." Around the American Hockey League, they called him "Moneybags." Today, a newspaper headline here trumpeted "Yes, We Ken."

Things have changed quickly for Linseman, whose overtime goal Monday night gave the Philadelphia Flyersa 3-2 victory over the New York Rangers and a one-up lead in the best-of-seven Stanley Cup quarter-finalseries that resumes here Wednesday night.

After recording one asist in his first nine NHL games, the 5-foot-11, 175-pound Linseman was demoted to Maine of the AHL, where he patiently rode buses for three months and tried to adjust his head to proper focus. Recalled March 1, he posted 24 points in the Flyers' last 20 regular-season games. Monday night, he was superb.

Linseman set up Bill Barber for the game-trying goal with 4:58 left in regulation time by outfighting RangerCarol Vandais in the corner. His game winner was an unassisted effort from the red line, in which he used teammate Barber and Rangers Vadnais and Pierre Plante as a moving screen before lining the puck behind goalie John Davidson.

Linseman passed up his final season of junior hockey at Kingston, Ontario, to join the Birmingham Bulls of the World Hockey Association. He scored 38 goals there last year and expected to duplicate that figure in the NHL. It wasn't until March that he got No. 1.

The Flyers paid Birmingham about $500,000 and handed Linseman a contract for another half million, besides using the first-round draft pick they obtained from the Rangers for releaseing Fred Shero from the final year of his contract. It was a big investment, but all the scouts said Linseman was worth it. He heard the talk and, at age 20, found the praise hard to handle.

A chipped ankle bone slowed him in training camp, but he admits it was a flawed attitude that hurt most.

"I didn't do anything right at the start," Linseman said. "I was never able to get the right feeling. At first, I was too relaxed. Then, later, i was too keyed up.

"If they hadn't sent me out, things probably would have gotten worse. They couldn't have kept playing me here. I had my condo. Ihad my condo. I was thinking too much about settling in and getting used to the surroundings, instead of playing.

"This was my goal, making it to the National Hockey League, and I had finally done it and it didn't occur to me that i had to keep playing hard to stay here. Besides, the adjustment was bigger than I expected. I'd never had any problems adjusting before. But here, I wasn't producing and I was getting scared."

Since he was placed between Barber and Paul Holmgren, Linseman has produced at a major-league rate. Monday, Barber had nine shots on goal, Linseman four. Holmgren provides them with skating room by tossing shots of a different kind. Unless the Rangers can slow these three, the New Yorkers will be headed for an unwelcome vacation.

Play also resumes Wednesday in Montreal, Boston and Long Island, with the home teams all one game up in series that figure to be less competitive than the Ranger-Flyer duel.

The Canadiens, pursuing their fourth straight Stanley Cup, have not lost to Toronto in the teams' last 17 meetings. Number 17, Monday, saw Montreal erase a 2-0 Toronto lead and breeze to a 5-2 victory.

There were more than 600 empty scats in the Forum, a factor attributable to local television and high ticket prices. But one can only wonder about the 2,600 empty chairs in Boston, where the Bruins thrashed Pittsburgh, 6-2.

Boston's Don Marcotte, a candidate for the Selke Trophy as outstanding defensive forward, was most offensive to the Penguins, with two goals.

Mike Bossy, the New York Islanders' 69-goal man, posted a hat trick in his first playoff test of 1979 as the league's top regular-season club demolished Chicago, 6-2, to extend the Black Hawks' record Stanley Cup losing streak to 13 games.