Rick Middleton's complexion is unusually pale, so his Boston Bruins teammates call him Casper. The Friendly Ghost is an apt term for Middleton in other respects, too.

For one thing, Middleton is too friendly for Boston Coach Don Cherry, who wants his wingers hitting people as often as possible. For another, Middleton keeps materializing near opponents' nets at crucial moments.

A year ago, in the first game of the Stanley Cup semifinal series against Philadelophia, Cherry ordered Middleton to score the winning goal in over time. The 5-foot-11, 170-pound winger obliged, with some assistance from Flyer goalie Bernie Parent, and the Bruins went on to a four-game sweep.

In Tuesday night's semifinal operner, again in overtime, Middleton suddenly found himself free in the slot, accepted Jean Ratelle's pass and beat Parent. This time, he was not under orders, Cherry commenting, "That was too much to expect."

Thursday, after the Flyers had wiped out a four-goal Boston Lead, Middleton appeared just outside the Philadelphia crease, completely unguarded and waving his stick to get puck-carrier Brad Park's attention. Park fed him, Middleton scored and the Bruins grabbed a 2-0 lead in the best-of-seven series. The series resumes tonight in Philadelphia's Spectrum.

Besides producing the winning goal Thursday, Middleton had connected earlier, faking defenseman Rick La-pointe inside, going outside and hitting the far corner of the net. Voted the game's top star, Middleton also made a superb play to keep the puck inside the blue line to set up a goal by Ratelle. Finally, just before he scored the winner, Middlton dove to block Jim Watson's slap shop from the left point.

"I know he got the winner, but I'm as proud of Middleton for blocking that shot as I am for his goal," Cherry said. "Of all the players I've coached, I haven't given anybody the guff I've given Rick Middleton. But give him credit. He took it and made himself into an all-round player."

As a junior at Oshawa, where he was a teammate of the Washington Capitols' Jack Lynch, Middelton led the Ontario Major Junior Hockey League in his graduating season with 67 goals. A first-round draft pick of the New York Rangers, Middelton spent his first professional season at Providence, where he scored 36 goals and was named the outstanding rookie in the American Hockey League.

Middelton's first NHL game coincided with the Capitals' debut and he connected twice in the third period to help the Rangers defeat Washington, 6-3. A month, later he scored four times against California. He was a leading candidate for rookie of the year, with 22 goals in 47 games, but a broken left leg intervened.