I SUPPOSE IT had to happen eventually. Someone had to combine the making-of-a-champion motif of Downhill Racer with the sentimental mawkishness of Love Story, and set the whole thing inside Maple Leaf Gardens. The result is what you might expect.

Billy Duke, rising Toronto superstar. Fast on his skates. A little slower with his mouth, but that's all right. He's honest, and his mind is clean. Sherri Lee Nelson, rising bubblegum folk singer. Well-scrubbed, blonde, vivacious. Smokes dope occasionally, but she's basically committed, one understands, to making this world a better place for all of us to live in.

"A story of two people...two worlds...one love. These two should never have been in love...but they were." This movie, Winter Comes Early, should never have been made...but it was. Unfortunately, we'll be stuck with it until someone finally decides to do a little more work and come up with an incisive documentary of ice hockey. Producer John Bassett, a Canadian sportsman with financial interests in both the Maple Leafs and the Toronto Argonauts football team, never really comes close.

Bassett's major mistake is that he even went anywhere near the story line of Love Story in the first place. In recent Boston newspaper interviews, he scorned Ryan O'Neal's performance in that film, saying that he had set ice hockey back several decades. It seems strange, then, that he would adapt the Love Story theme almost in its entirety for what he hoped would be a fresh, penetrating look at one of the two most violent games in the world.

Duke's life story begins, as they all do, on a frozen lake somewhere in the backwoods of Canada, where his father is calmly, patiently instructing him on how to keep his little four-year-old ankles straight, shift the puck from side to side and let that slap shot go. Father Duke dies, but his creation lives on, and we watch him go from Squirt to Pee Wee to Midget to Bantam to the Junior Leagues, and finally, as Derek Sanderson looks on, to a triumphant performance at Toronto and the OHA championship.

Sanderson and his agent fight their way into the jubilant locker room later, and arrange to meet Duke at the Hub, a downtown discotheque. There, the fateful relationship begins. Duke, the future professional star, meets Sherri, the Ontario Melanie. If you saw Love Story, you know the rest. The Maple Leafs, desperate for a forward who can breathe some life into their faltering team, draft Duke as their first choice, and thanks to some crafty bargaining by Sanderson's agent, agree to sign him to a $120,000 contract for two years. Sherri, meanwhile, has progressed above the club circuit, and rapidly becomes more popular than Clearasil with the youth of Canada. The two meet again at a promotional event, and Duke persuades her to attend one of his games. She does, is repelled by the violence, the horrid signs (Leafs are out to KILL!!!), and Duke's presence in the penalty box. They both split on tours, but Sherri just can't forget Billy Duke ("I'm younger, stronger and tougher, and that's why you dig me," he says.) When he is hospitalized following a brawl at Los Angeles, she flies to his bedside, and from that point on, they are inseparable. They go for walks, gambol in the snow, kiss a little. All that. But then things start going sour. Sherri becomes depressed by the constant touring, the gigs, the promotional hassles connected with folk-rock stardom. "There's nothing inside it to hang on to," she says. "Everyone should do their own number. There's enough hate around, right?"

Yet she can't quite reconcile herself to the hockey world, either. No one connected with the game seems to realize that all that violence is sickening, least of all Duke. And the longer you stay with hockey, the more callous, more insensitive it makes you. One afternoon, while Billy and Sherri are frolicking in the woods, he sends his dog after a rabbit, and expresses no remorse when the smaller animal is killed. Things get rocky from that point on, and when the Maple Leafs' general manager tells Sherri that in hockey, "everything has to be put in its proper place, even a wife," the damage to the relationship is irreparable.

TORN BETWEEN her love for Billy, and her dedication to peace, Sherri drops acid to clear everything up. Under the circumstances, it is a reasonably unwise thing to do, and she pays for it, lying moaning for a few days in a Toronto apartment while her friends move on to San Francisco for another gig. Duke, meanwhile, goes to pieces, athletically, and the Maple Leafs stagger downward in the NHL standings to the point where they must defeat the Vancouver Canucks in the season's final game to qualify for the Stanley Cup playoffs.

Toronto coach Freddy Wares, his job on the line, establishes a 9 p.m. curfew on the night before the big game, but Duke breaks it to keep a rendezvous with Sherri. He is subsequently caught by Wares, who immediately suspends him, and banishes her to the open road. Moments later, she is killed in a flaming auto wreck, and Billy is crushed. He wanders aimlessly around the Toronto streets, his mind a kaleidoscope of romantic flashbacks. Sherri is gone. But the game lives on, and the next night, with Toronto trailing by two goals late in the game. Duke strides down the runway at Maple Leafs Garden, patches things up with the coach, and enters the fray, presumably in time to turn the hat trick and save Toronto from elimination. Thankfully, we'll never know.

If the above sounds implausible to you, you're not alone. Yet, Bassett's original idea--to present an actual picture of life as it is around the National Hockey League--could have been salvaged. Several times, he comes close to saying something significant--about the player-agent alliance that is presently causing so much friction between labor and management, about the way a pro hockey team functions internally over the course of a season, about the contrast between aging veteran and brash rookie. But he prevents himself from covering any of these in depth by saddling himself with the hokey Love Story angle.

It would have taken a much more talented cast than Bassett recruited to bring off this documentary-romance melange with even a trace of facility, and such deserved unknowns as Trudy Young. Art Hindle and Frank Moore just can't handle it. The acting is wooden and emotionless, and George Robertson's screenplay doesn't help. The dialogue, plainly, is awful. For example: Billy, after meeting Sherri, "Hey, is she for real?" Friend: "Yeah." Maple Leafs' general manager: "What do you think of us, the hockey world?" Sherri: "Well, it's different, ya know?" GM: "Yes, different, and very special." The level of repartee never gets much higher. Actually, the best piece of acting in the whole damn picture is turned in by Sanderson, who is the nearest thing the Boston Bruins have to a member of the Socially Prominent. He is, sadly, the only cast member that seems at all at home in front of a camera. No one will ever accuse him of being a Gable incarnate, but the two minutes or so of stage time he is allotted comprise the only light, humorous touches in the film.

ALL OF WHICH is disheartening, because Cannon Group, Inc., invested a large sum of money and a good bit of time putting it together. There is some good action footage from NHL games that includes nice cameo shots of Stan Mikita, Jean Beliveau, Gordie Howe, and Bobby Orr and an impressive brawl between the Maple Leafs and Los Angeles Kings that apparently was caught by accident.

But the footage and the script don't join at all, and the effect is jarring. We are told that Duke is a superstar, but we are rarely given closeups of him in action. We are told the Maple Leafs fall apart as the season goes on, but we never see the disintegration. This is part of what Bassett has to do in order to create a valuable and lasting statement about the sport, and he sidesteps his responsibilities either by design or neglect. Such a statement can be made. Robert Redford came fairly close to it in Downhill Racer, and Bruce Brown presented creditable efforts on bike riding and surfing in On Any Sunday and The Endless Summer, Winter Comes Early doesn't measure up to these, however, and theatre entrepreneur Ben Sack seems to sense it. In his advertising, he stresses the appearance of Derek Sanderson and the Boston Bruins, though they are present for maybe four of the film's 100 minutes. It's promotional hype, of course, and probably a rip-off, since the admission price is $3. You're better off buying a seat in Boston Garden, sitting with the Gallery Gods, and trying to sort out for yourself what the game is all about.