Professional baseball forms the setting for a realistic, sometimes touching comedy-drama that could find great favor with the public. Except for biographical films, sports movies haven't always been popular at the b.o. Additionally, baseball is no longer the nation's number one spectator sport. With these hurdles to overcome and the lack of star names, the main ingredient becomes the story itself. Produced by Maurice and Lois Rosenfield, the Paramount release is sure to garner a wealth of critical praise that will help get the message across. Mark Harris' screenplay, based on is 1956 TV drama (with Paul Newman and Albert Salmi), is a fictionalized account of what might happen to a big league New York baseball team if one of its key members were suffering from a fatal disease. The actors and director John Hancock capture a real feeling for the game and its particular sidelines, e.g., the players' constant needling of each other, their outside interests, their philosophies. As in the current "Maurie," Michael Moriarty devotes his time to the interests of his dying friend. Title is from the song "Streets of Laredo," the film's theme. Filmed in New York and Florida, color by Movielab. Paramount. 97 min. Starring Michael Moriarty, Robert DeNiro, Vincent Gardenia, Phil Foster, Ann Wedgeworth and Patrick McVey