It is the eve of the October classic in which America's annual love affair with baseball comes to its bittersweet end, and Robert Redford is nearly ankle-deep in mud on a chilly rain-soaked baseball field in Buffalo.

He's working, appropriately enough, with two Baltimoreans to put the essence of that eternal infatuation with bats and balls and bases on film.

Barry Levinson ("Diner," "Best Friends") and Caleb Deschanel ("The Black Stallion," "The Right Stuff") are director and cinematographer, respectively, of "The Natural," the dramatization of Bernard Malamud's 1952 novel about baseball and the lure of immortality.

It is Redford's first acting role since "Brubaker," a prison drama released in 1980, and it probably is his last chance--at the age of 46--to play a 34-year-old rookie. He has acknowledged as much. Asked at the beginning of filming in August why he chose to make a movie about baseball, he replied, "The meter is ticking."

As Roy Hobbs, the mysterious and magnificent unknown player portrayed by Redford, observes in Malamud's novel, "If you leave all those records that nobody else can beat--they'll always remember you. You sorta never die."

In movies, the record book is film, and what takes place in front of the camera--no matter how masterful the guiding hands behind it--is what the public sees and remembers. The images never die.

So Redford, surprisingly lithe--almost wiry--in person, has been tossing balls, running bases and taking practice swings with young actors and ballplayers half his age on the field of Buffalo's splendidly seedy War Memorial Stadium, a WPA project completed in 1937, the year he was born. It is called "The Old Rockpile" by natives.

Redford was a tournament-winning tennis player in high school and earned a baseball scholarship to the University of Colorado. During rehearsals he has walloped several 300-foot home runs, and the film's technical adviser, New York Yankee batting-practice pitcher Tony Ferrara, syas Redford has " 'natural' ability, if you'll pardon the use of the word."

But Redford may well have explained why he became a movie star rather than the member of a baseball team when he said: "In high school I began to suspect the idea of team spirit, the attitude that it wasn't whether you won or lost but how you played the game. The only kick I got out of it, I realized, was if I hit a home run . . ."

Nevertheless, to some extent, the film is enabling Redford to fulfil a childhood fantasy.

He likes to point out that his father taught him how to play baseball and the American tradition of fathers passing down a love of the sport to their sons is a central theme of the movie. It is not a theme at all in the book, and purists may be unhappy with the discrepancy.

"I think Malamud would not be pleased if he read our script," conceded Mark Johnson, the film's 36-year-old producer. "But I think audiences would be disappointed if we followed the somewhat cynical line of the book. We're doing more of a fantasy along the lines of 'The Black Stallion.' "

There are fantasy, myth and baseball history aplenty in Malamud's book, but its overall mood is black and its ending is tinged with tragedy. The movie's ending is decidedly upbeat.

The book contains fictionalized versions of episodes drawn from the comic, tragic and strange lore of baseball: former Oriole Wilbert Robinson's effort to catch a grapefruit dropped from an airplane; the stumble by Detroit Tiger Chuck Hostetler between third base and home plate that cost his team the sixth game of the 1945 World Series; the shooting of Philadelphia Phillie Eddie Waitkus by a deranged woman in a Chicago hotel in 1949; a potentially disastrous, gluttony-induced stomachache that hospitalized Babe Ruth in 1925; and the 1919 White Sox scandal in which players were bribed to throw the World Series.

The character Redford plays is a promising 19-year-old pitching prospect on his way to a tryout with the Cubs when his dream of stardom is shattered by a mysterious temptress he meets on the train who lures him into a hotel room and shoots him in the stomach.

He spends the next 15 years in a variety of pursuits, all of them failures. At 34, he returns to baseball, and switches from pitching to hitting (as did Ruth) and joins the down-and-out "N.Y. Knights," bringing along his homemade bat--"Wonderboy"--the modern Excalibur and Arthurian lance, as the late Earl R. Wasserman, a Johns Hopkins literary scholar, observed in a witty analysis of the book in 1965.

"By drawing his material from actual baseball and yet fusing it with the Arthurian legend, Malamud sets and sustains his novel in a region that is both real and mythic, particular and universal, ludicrous melodrama and spiritual probing--Ring Lardner and Jung," Wasserman wrote.

In the book, evil triumphs. Aware that his health will not permit him another season, Roy Hobbs is tempted by the offer of a bribe to betray his teammates and throw the pennant-clinching game. He changes his mind during the course of the game but strikes out anyway. The bribery is uncovered by a slimy, cynical sportswriter (played by Robert Duvall in the film), and the novel ends with a small boy wailing at the tearful Hobbs--as a child he was said to have pleaded with the White Sox's Shoeless Joe Jackson--"Say it ain't so!"

In the movie it won't be. Redford/Hobbs is not a chump and manages to redeem his father's dream.

The combination of legend and Redford, along with prizes, has drawn thousands of extras to sit in the rainy stands with temperatures in the 40s and pretend it's the middle of summer.

The night he had to make the final and crucial trip to the plate, Redford appeared from beneath the stadium stands, where he spent much of his off-camera hours sequestered in a 30-foot-long private house trailer and dressing room. He took the assistant director's microphone and offered his "sincere appreciation" for the cooperation and friendliness of much-maligned Buffalo.

"And just don't hold it against me as I strike out tonight," he added in response to their applause and whistles.

They didn't, of course, as he whipped the air with futile swings and obligingly laced a number of long drives foul, each of which was greeted with appropriate gasps of anticipation from the crowd, followed by well-acted groans of disappointment.

The script called for a burst of fireworks at the finale, and around 4 a.m. a band of pyrotechnicians set off explosives that showered the cast and crew with sparks, ruining the assistant director's jacket.

If the end of the film version of "The Natural" is unfaithful to the original, rejecting its theme that superb abilities cannot overcome a flaw in the human spirit, it still remains true to a key element of the sport it reveres: baseball's triumph over time.

Roger Angell, The New Yorker's baseball laureate, has called "The Natural" the best novel ever written about the game. The young Hobbs does not replace an aging slugger he strikes out at a county fair while on the way to his aborted tryout; in time he becomes the aging slugger. The transformation captures something at the core of the sport's appeal, Angell observed: "Baseball players are seemingly young forever."

Sorta like in the movies.

Neil A. Grauer is the author of "Wits and Sages," a book about syndicated columnists, which will be published next spring. graphics/photo: Robert Redford: 'In high school I began to suspect the idea of team spirit, the attitude that it wasn't whether you won or lost but how you played the game..."