If there is a key to the utterly unpredictable baseball playoffs, then it may rest in the minds of the Kansas City Royals and Philadelphia Phillies -- those clubs whose whole team identity is tied up with their playoff losses in 1976, '77 and '78 and their collective efforts ever since to exorcise those demons.

Odd as it may seem, baseball teams believe the mythologies that grow up around them. Perhaps they only half-believe, like men on a dark night who keep glancing over their shoulders. They know nothing malevolent is there, but they keep looking. And if something should appear, they jump twice as high.

The playoffs are baseball's horror chamber -- the place where it is easiest to get scared out of your double knits. If you believe in ill luck or jinxes, don't go near the playoffs. Every baseball act there carries double or treble weight. Nothing is fair. Everything is sudden and ineradicable.

That is why the Phils and Royals must defeat their own ghosts before they can beat their tangible foes and reach the World Series. These are teams that need a designated shrink to help them overcome their inferiority complexes. Don't scoff. Both towns and their teams have much to overcome.

All season, Kansas City's veteran leader, Hal McRae, has been asked if these '80 Royals are the best ever. The conventional answer is an upbeat, gung-ho, "Sure we are. We never had (lead-off wizard) Willie Nelson or (submarine reliever) Dan Quisenberry before." But McRae can't bring himself to say it; he bites his tongue, over and over, and says, "Only if we win the playoffs."

And in Philadelphia last Saturday, Mike Schmidt was asked if this division title were the sweetest. "Only if we get to the series," he said, "Otherwise, we're just the same old Phillies."

Most teams try to reason objectively about themselves. The Baltimore Orioles, for instance, after winning their 100th game, broke out the champagne as visible evidence of their self-evaluation that they are perennial winners, no matter what the standings say they finished second this particular year. But the Royals and Phillies reason backwards. They let a best-of-five playoffs -- the most capricious conceivable arrangement -- tell them whether they should think of themselves as "winners" or "losers" (those deceitful terms).

As the Phillies celebrated their division clinching on Saturday, Tug McGraw, in the midst of several screaming Phils, opened the first symbolic bottle of champagne. Or, rather, he tried. The cork broke off in his hand. He was left with a bottle that was impossible to open. The collective gulp was almost audible . . . nervous laughs . . ."Hope that doesn't mean anything."

In Philadelphia, the ghosts that are most feared are within the Phils themselves -- part of an incredible team antitradion that says this franchise has never been world champion since inception in 1883 and that it has not won a World Series game since the opener in 1915.

Who believes such superstitious junk? Weeeeeeell . . .

"I feel a little sorry for the Expos," said Schmidt, after Montreal was eliminated on the last weekend of the season for the second straight year, "but they're going to have to go through another year of frustration before they're as frustrated as the Phillies."

The Phils enter the playoffs in their customary state of civil war. The difference this time is that out-front Manager Dallas Green has spent the whole year blasting his team publicly dozens of times for lack of team play, selfishness, absence of alertness and (his favorite phrase) "putting 'me' ahead of 'us"'

As Green stood on a press conference podium on Saturday, several Phils lurked behind him, as though eavesdropping. "They know my penchant for ripping my players publicly," said Green, who earlier in the week, had said, "10 percent of this team is a cancer and it will be cut out before next year."

"We're the only team that flushes its mind in public," said McGraw.

Oh, if only the Phils really could purge their minds. Then they could forget how the Reds swept them in '76. They could forget Manny Mota's liner in the ninth inning of the 'pivotal' third game in '77 that Greg Luzinski missed in left field when Manager Danny Ozark neglected to put in defensive replacement Jerry Martin. And they could forget the simple 10th-inning line drive that Gary Maddox missed to end the '78 playoff in Los Angeles. The gleaming white accusatory ball sat untouched in the Chavez Revine grass as the dazed Maddox jogged off, running right into the middle of the Dodger's back-slapping celebration.

If the Phillie hauntings are internal, then the Royal monsters always wear pin stripes, just as they will again this year. If W.C. Fields and his dumb jokes are Philadelphia's undeserved badge of second-class city-zenship, then those Yankee uniforms are the emblem of all Kansas City's years as a New York farm club.

No club hates another club in baseball as intensely as the Royals hate the Yankees. And a bit of vice versa, too. These teams love to rub each other's noses in the dirt -- they run up the score at every opportunity. This year, K.C. has ripped the Yankees, 12-3, 13-1, 14-3 and 8-0, while the Yankees had an 18-3 win. Sportsmanship? What's that? the Royals ask.

Was it sporting of Chris Chambliss to hit a pennant-winning homer in the bottom of the ninth of the fifth game in '76 off their Mark Littell, who had only allowed one homer all year? Was it sporting to score three runs in the ninth of the fifth game in '77 when the Royals were three outs from the World Series? And was it sporting in '78 in that fulcrum of a third game to ignore three homers by George Brett off Catfish Hunter and win anyway?

The Royals don't forget. They have Yankees on the brain. Some say it will be their biggest hindrance. "Right now, we know we are a better team than they are," says Brett, who in '78 out-slugged Reggie Jackson head-to-head, 1.056 to 1.000. "We beat 'em eight out of 12 this year."

Both the Royals and Phils are capable -- at least in the abstract -- of reaching the Series this year. If nothing else, they have new unscarred managers. How could the Phillies ever win with Danny Ozark and his look of eternal perplexity, curled up, arms crossed in the dugout corner like a totem of defeat? And the Royals always thought Whitey Herzog panicked with his pitching changes against the Yankees; to wit, using five pitchers in the space of seven batters in the denouement of the '77 fifth game.

This is the year when, at least, the Royals and Phils have the correct idea of how to beat a playoff foe. They just have to do it. The Royals' 8-4 record against New York reflected their understanding that a team must build early leads against the Yanks, whose mega-bullpen has preserved 76 of 78 leads from the seventh inning on. The destructive opening bid of Wilson (230 hits, 79 steals), McRae (currently hot) and Brett (.390) usually bats three times in the first five innings. The extent of their damage may determine K.C.'s fate.

The other key may be the ability of mush-balling submariner Quisenberry to be as underwhelmingly efficient as Goose Gossage is overwhelmingly effective. Unbeknownst to most, Quiz has 45 wins and saves to Gossage's 39, though no sane person would trade Gossage for Quisenberry. Oddly, the right-handed Quisenberry is generally better against lefties, producing grounders, which could help with the final three games scheduled for Yankee Stadium's short right-field porch. However, one exception to the rule is Jackson, who often aces the Quiz with ease.

The underdog (7-5) Royals, however, cannot feel a fraction of the genuine confidence against the gutty, resourceful 103-win Yankees that the Phillies can muster against Houston. If ever one team silently prayed for another to hang on, it was the Phils rooting for the Astros not to blow four straight season-ending games to the Dodgers. Los Angeles' track record against Philadelphia is history, particularly the strength of righties named Davey Lopes, Ron Cey, Steve Garvey and Dusty Baker against Steve Carlton.

The Phils, by contrast, have owned the Astros, winning nine of 12 this year. Carlton, rested and ready to start twice if necessary, pitches some of the quietest games on record against the lefty-heavy Astros. Dick Ruthven is 3-1 against Houston. Even the Astrodome, Houston's secret weapon, has not usually bothered the Phils since its emphasis on defense and speed suits the current fleet-footed, fine-fielding Phillies who, Mike Schmidt aside, are not a team built on power. Star reliever McGraw also finds the Houston order a calming thought.

And, historically, calming thoughts are what both the Phillies and Royals need most in October.