This is an old-fashioned, cornball success story about a new mover and shaker in baseball known as "Trader Jack."

In less than two years, he has transformed the San Diego Padres from a bunch of overpaid, malingering lumps into a young, hustling contender that at the All-Star break has the second-best record in baseball.

It's a story about a tough, career baseball guy named Jack McKeon who, after the age of 50, finally got the chance to be the boss, the general manager, instead of the guy taking all the orders.

The silk-suit front-office guys all thought they'd slicker this overmatched pigeon; they couldn't wait to beat the sawed-off former bush-league catcher in the back-room trades. The Smart Money listened to McKeon as he said "ain't," cussed a blue streak, chewed his cigars and acted just a little dense. They mistook him for a mark when he was the one running a game.

Everybody laughed at him, put their hands over their eyes, when he traded Rollie Fingers and Gene Tenace for unknowns and told free agent Dave Winfield to go ahead and leave town 'cause who needed him, anyway? "We had a lotta bad actors," he says, naming no names. "Good riddance."

McKeon, appointed general manager in September 1980, made a dozen deals so fast that nobody had time to figure out what he was up to. That is, until this spring, when everybody who lost to the Padres began to realize that 17 of their 25 players were the nobodies McKeon had stolen in those trades. Seven of the eight Padre regulars, three of four starting pitchers, plus one bullpen ace and most of the bench were discount players McKeon had grabbed in 15 months.

Slowly, the pieces formed a picture. McKeon had hornswoggled George Steinbrenner out of four young major leaguers, two of them of all-star quality, in exchange for just one decent player. Next, he'd stolen the smart, hard-nosed manager he wanted--Dick Williams--right out from under George III's nose. Then, McKeon had gone to the winter meetings and come away with the two moody stars that everybody wanted, Garry Templeton and Sixto Lezcano; but McKeon was the one who got 'em.

All those amusing Padre deals in the fine print--goofy, trivial stuff like Salazar for Bevacqua, Bonilla for Lacey, DeLeon for Olmstead, Wiggins and Montefusco for nothing--suddenly proved to be the sounds of a franchise being rebuilt.

But, above all, this is a story about the big payoff--Jack McKeon's reimbursement for a lifetime. San Diego's 50-36 record and its swelling attendance might as well be a gift from the baseball fates, inscribed, "To Jack, for services rendered."

This is the payback for all those lonesome years in hotel rooms away from his wife and four kids, seeing 300 games a year in person. All those unknown players that this unknown man saw in all those unknown places were tucked away in the corners of his memory.

When the big-timers gathered 'round to take him to the cleaners, McKeon just let 'em keep talking until they began mentioning the raw diamonds they didn't even know they had. Then, one by one, he picked their rich pockets. "Always let the other guy be the first to mention the player you really want," he says.

" . . . I've never said I was smart, but I'm not afraid of work and I'm willing to take a chance."

It's out of character for McKeon to be the center of a flashy success story. Even now, they can't drag him out of Lodi and Amarillo and Walla Walla and all those bush burgs where he learned what he knows. Like the man says, "I gotta work even harder. They're on to me now."

For 33 years in baseball, McKeon's always gotten the dirty jobs. As a player, he was a squat, burly backstop in the Pittsburgh organization. That means he never got very far. To feed the family, he looked for forms of baseball employment even tougher than catching. For half a lifetime his job description changed with the seasons: coach of every kind, itinerant scout, scouting director, farm director, assistant general manager, field manager in 13 major and minor league cities.

That doesn't count the six winters managing in Aricebo, Puerto Rico. They called him "the Mayor of Aricebo"--kind of an inside joke, like being the governor of Siberia. The hot-prospect managers work the Condado strip in San Juan and wear the white dinner jackets in the casinos. Arecibo is poor, remote farming country. But McKeon liked it fine. Kept going back.

These days, McKeon only wears one diamond ring, and it's not from a World Series; it's a huge thing with about 25 diamonds set in a square that looks like, when it grows up, it'll be the first set of diamond brass knuckles. Worth a bundle. "The people of Arecibo gave it to me when I left," McKeon says proudly.

At 51, McKeon's one undeniable genius may be his gift for self-effacing anonymity. Ask the best of fans this puzzler: who, in the last 10 years, spent five seasons managing Oakland and Kansas City, and is now general manager of San Diego? Hint: as a manager he finished second twice. It would suit McKeon fine if his headstone read, "Here lies a good baseball man."

"Let's see, are there 365 days in a year?" he asks. "Then I'm in a ballpark 300 of those days. High school, American Legion, college, minors, winter ball, instructional league. I probably see another 200 to 300 games a year on TV or cable. You never know when you'll notice something.

"What I do best is judge talent. But I can't explain it. It's just my guts tellin' me. I can see the talent inside, even when it hasn't come out yet."

The McKeon Method is always the same. He saw Salazar, then Pirate property, in the Eastern League; in 1980-81, Salazar hit .313 as San Diego's third baseman. McKeon saw Juan DeLeon, then a Cardinal farmhand, in Puerto Rico five years ago; now DeLeon has a 1.76 ERA in 27 games for the Padres. McKeon saw Alan Wiggins (28 steals this year) play one game for Class A Lodi; "If I hadn't seen that game," says McKeon, "he'd still be a Dodger today."

McKeon, then manager of the Kansas City Royals, used an off day in '74 to see the San Jose Bees play the Fresno Giants; he spotted Ruppert Jones. Six years later, McKeon held up a trade with the Yankees for two weeks until Steinbrenner put Jones (now an National League All-Star) into the deal, not Bobby Brown.

"I knew Rupe was bona fide. There was another Yankee I wanted, but I didn't want to blow it by being a hog." When you've taken their shirt, always leave 'em a loincloth; you might want to come back and steal that, too, someday. As it was, McKeon got Jones, Tim Lollar (10-2), left-hander Chris Welsh (5-3) and Joe Lefebvre for Jerry Mumphrey.

These days, McKeon hasn't changed style. "Going to Reading and Hagerstown to see a couple of games," says McKeon, even as he sits in Philadelphia's Veterans Stadium with his wife ("She's got a good eye for prospects"), watching his club beat the Phillies. "I like to talk to our (minor league) kids, let 'em know somebody cares."

That, McKeon is told, isn't usually the way major league general managers work.

"I don't know how to play the big shot," says McKeon, whose biography gets one paragraph in a Padre media guide in which minor leaguers get two pages. "I can't rest on my laurels, because I didn't come here with any laurels."

Has such success surprised him? After all, the Padres are a 13-year joke.

"I'm not surprised at the results, just the speed at which we've reached 'em," says McKeon. "We're six months ahead of schedule."

Even if it took only 33 years to get there.