A couple of years ago, Jack Nicklaus blew the Inverrany Golf Classic - just threw the tournament away on the finishing holes.

Nicklaus calmly signed autographs, gave a gracious mass interview, congratulated the winner, then marched quietly into the office of his old friend, John (Moose) Montgomery, the director of the tournament.

Nicklaus shut the door and proceeded to destroy everything in the room. He smashed furniture and ripped the walls bare of pictures. When the joint was completely totaled, Nicklaus opened the door and walked out, smiling as serenely as when he had entered.

One of the most influential men in golf - a close friend of Nicklaus for over 20 years - tells this story with delight. But it is the punch line of the parable that fascinates him.

"Moose might have destroyed a bar or two in his day," said the friend, explaining why Nicklaus had choosen Montgomery's office for destruction. "But no one, not even Moose, ever figured out if Jack was really mad, or if it was just his idea of a practical joke."

The fires that burn inside Jack Nicklaus are well hidden. No golfer has ever seemed more composed and methodical under pressure, nor more magnanimous in defeat. Shakespeare's words - "He who would be calm must first take on the appearance of calm" - might be Nicklaus' motto.

Yet at times Nicklaus' calm seems to run so deep, his generosity seems so genuine, and his natural candor seems so irrepressible that it is easy to wonder if Nicklaus the man isn't even more interesting than Nicklaus the golfer.

These are supposed to be difficult days for Nicklaus. The Golden Bear must go into hibernation this winter with bad thoughts on the brain pan. He's 37 and they're saying those ugly things about him again - Jack's feeling his age, losing his edge. He can't beat the kids in the big ones.

Yet Nicklaus hardly seems to notice all the talk about his inevitable decline. His self-assurance and self-knowledge are a legend among pro golfers.

"If Nicklaus says an ant can pull a bale of hay," says Lee Trevino, "then hitch him up. Jack don't say nothing he doesn't mean and he doesn't know what it is to life."

Nicklaus own evaluation of his year is so disarmingly simple that from any other apparently sagging star it might seem like self-delusion.

"I've been this close to having my best year," says Nicklaus, holding two fingers a millimeter apart. "I mismanaged my schedule in the middle of the summer and I've gotten tired of golf for the first time in a long time."

"Jack's got it doped about right, I guess," says Trevino. "He looks exhausted to me. His legs don't have that snap, so his hands catch up too soon and he comes over the top of the ball and pulls it left."

if Nicklaus had one final chance in 1977 to act like a sore loser, or resemble a fading beauty queen, it came in the recent World Series of Golf.

Instead, he came out looking like a true monarch of his sport. Few men have been so gracious in failure.

After a triple bogey during the second round had virtually ruined his chances of either a first or second-place finish, Nicklaus trudged into the press tent to relive the nightmare and answer questions about the final disappointment of his most frustrating year.

Before he could say a word, a can of (frozen-solid) soda in his hand fritzed all over him. Without missing a beat, Nicklaus looked at a reporter who always asks him needling questions and said, "Peggy, did you do this?"

After he had wiped the syrupy stuff off his face, Nicklaus refused to throw away the frozen soda. For nearly 15 minutes while he answered questions, Nicklaus thawed the can with his hands and little by little filled a glass with cola - a dribble at a time.

It was typical of the frugal, somewhat obstinate and infinitely patient Nicklaus to finish what he started, even if he could write a check for a million more cooperative cans of soft drink.

Nicklaus has reached a point at which he is so relaxed and confident in his world that no jack-in-the-box can make him jump. Where other athletes are nervous and strung out in the perpetual spotlight, Nicklaus means it when he says, "I love everything about the life on the tour. I hate to even think about the word 'retirement'."

In crowds - and Nicklaus near a golf course is a man constantly surrounded - the Bear seems as old-shoe as everybody's brother-in-law. Luckily, he does not have Arnold Palmer's charisma. No one screams or faints in his path. The gals in short-shorts with the credit-card eyes give him the hungry look and get nothing back.

Walking awat from the practice range last week after kibitzing his way through a few dozen shots, Nicklaus signed autographs calmly patted kids on the head like they were his own five and called out to Angelo, his caddie, "Hey, Ange. Don't forget ya got my wallet and room key in your bag."

Nicklaus and his wife Barbara have mastered the trick of blocking out the world that is staring at them. On an elevator at a Holiday Inn, Nicklaus punched the 10th-floor button. Then, as the elevator started to stop he jumped forward, struck a comical pose and stuck all 10 fingers in the crack of the doors and started trying to pry them apart. "Hey," he said to Barbara, "This is the floor where the doors stick, isn't it?"

They got out - he grinning like a fraternity man who has just pulled one of his cute little moves on a first date, she poking him in the ribs.

Around other players, Nicklaus walks softly, unobtrusively. Where most athletes seem cliquish, more comfortable with their own kind, Nicklaus is just as at home with nonathletes. He likes conversation more than macho grunts.

Nicklaus looks intently at those around him, concentrating on the details of their faces.

Sitting in the Firestone Country Club locker room, he saw a news clipping about NFL stars O. J. Simpson and Bob Griese both having blurred vision.

"I always thought there was something strange in O.J.'s eyes . . . like they didn't quite focus perfectly. Ever notice that?" Nicklaus said. "Griese's eyes are very acute," he added, making a gesture like a person threading a needle. "He always looks like he doesn't miss a thing."

Next, Nicklaus' eyes caught a local newspaper headline. "Nicklaus Misses 'Moving Day'," he read. "What in the world is 'moving day?'"

He was told it was a term among younger players for the third round of a tournament in which everyone frantically shuffles position, shooting themselves into or out of contention.

"I shot 68 yesterday," he said softly, with that enigmatic little-boy smile, as though he had done something very bad. "I guess I should have shot 60."

Then Nicklaus looked at a clock and hopped up. "I'm going to chat right through my tee-off time," he chuckled. "I guess I better shoot that 60 today." Then he added, with obvious disgust over his back-in-the-pack position, "That's about what I'll need."

If Nicklaus has finally mastered the ability of relaxing around people, whether they are fellow players, press, gallery or just people who want to speak to him, he still has amazing powers of concentration.

Once Nicklaus could not do both simultaneously. "It's easy for some people to smile - it just comes natural to them. For me, it's a project," said Nicklaus when he was 25.

"Must be my face or something, but I have to bring new muscles into motion when I smile."

The transformation from those uncomfortable, unpopular days- when he was called "Ohio Fats" and "Baby Beef," and the crowds of Arnie's Army rudely cheered when he missed shots - is long since completed.

Nicklaus has overcome it all. "People forget what he had to do," says golf commissioner Dean Beman. "I can't think of any one who had such an image preoblem in any sport. People just couldn't see what kind of person he was underneath. All they saw was a big, chunky kid with a lot of power beating the great Palmer.

"Jack might have been cheated of his due in this sport if he had not done five times as much to force people to acknowledge his greatness. If he had just won four or five major tiltes, he might have been lost in the shuffle. People outside the game were very slow to give him credit."

To this day, Nicklaus responds to the second-fiddle-to-Palmer digs with sharp humor. Last week at a ceremony, Gary Player said, "I was privileged to play in the first World Series of Golf in 1962 with the great Arnold Palmer."

Hundreds of people winced, knowing that it was Nicklaus, then a rookie of 22, who had won that first head-to-head-to-head showdown of the thenBig Three.

Player never mentioned Nicklaus in his talk. When the Golden Bear got up, grinning mischievously, he began, "I, too, was privileged to play in the 1962 Workd Series with that great man, Arnold Palmer."

The crowd broke up and Player hung his head, laughing, too.

Those who have known Nicklaus for years say that he has hardly changed at all with growing fame and wealth, but that he has managed to show more of himself to the public each year.

"Jack has never forgotten his old friends," says Beman. "His chums as a boy in Columbus, his buddies form Ohio State; they are still among his best friends. He moves in different spheres now, but they're still comfortable together."

The obituaries for Nicklaus should start rolling in any time now. It happens every time Nicklaus has an "off year" by his high standards. It happened before in 1968, 1969 and 1974.

"I don't see any significant slipping in any part of my game," says Nicklaus, who would probably be the first to admit it if he did. "I just had a lot of frustrations this year."

"People forget that Jack has the lowest stroke average on the tour again this year." points out Trevino. "Tom Watson is second."

As Nicklaus moves toward 40, his place in golf grows while his skills must inevitably diminish. The man behind the bearish drives a figure worth considering long after any shot he ever hit is forgotten.

"Jack Nicklaus was blessed with good parents and a good wife," says UGA official Joe Schwendeman. "But even with all his good fortune, he has been a rare man. He has lived a life that will bear serutiny."