The most remarkable aspect of the National League playoffs isn't that the San Francisco Giants are ahead by a game but that this pennant debate is still in progress at all. The St. Louis Cardinals, who should be on vacation now, still have breath, hope and, believe it or not, several factors on their side.

Every break conspired last week to give the Giants a chance to stomp the Cardinals in five games and clinch at home in Candlestick Park. The Giants showed spunk, rallying from a raw loss Friday. They're bona fide favorites now. But does anybody else hear spooky organ music?

All weekend the Giants slapped themselves on the back, perhaps trying to hypnotize themselves into believing they're a true pennant outfit, even a potential world champion.

Certainly you will not find athletes cockier than Will Clark and Jeffrey Leonard. Or managers with a more assiduously cultivated mystique than Roger Craig -- the Fox. Or veterans who talk better about "missions" and "making history" than Bob Brenly and Mike Krukow.

Still, it's worth noting that two months ago the Giants were a mediocre team (54-55) until trades for Kevin Mitchell, Rick Reuschel, Dave Dravecky, Craig Lefferts and Don Robinson filled executive Al Rosen's inside straight.

Solid as these guys are, none is headed to Cooperstown. The Giants emphasize their teamwork and lack of superstars. That's wise. They don't have a single player with: 90 runs, 95 RBI, 30 doubles, 20 steals, 15 wins or 20 saves. This is a versatile, resilient and cohesive team with a flash-fire sense of destiny. The Giants can do some of everything and hit plenty of homers. But they're still a 90-win club (sixth best in baseball) with no dominant starter or reliever.

To be fair to the Cardinals, let's ask how the Giants, who are in perfect health, would have responded if they had faced St. Louis' injuries.

What if Will Clark (eight for 18) were out, rather than Jack Clark? What if switch-hitting Chili Davis, not Willie McGee, had a bum wrist and was useless batting right-handed? What if Kevin Mitchell, not Terry Pendleton, missed a game and now played at half-speed? What if Rick Reuschel, not Danny Cox, had been a last-minute scratch in Game 1, throwing the Giants' rotation in the air? What if Dave Dravecky, not Greg Mathews, had left with an injury after three innings even though he had a lead?

The Cardinals may be the grittiest team of the '80s. They came from 3-2 behind to win the 1982 World Series. They came from 2-1 down to win the '85 playoffs. Yes, they let Don Denkinger's bad call kill their spirit in the '85 World Series. But they're still tough customers. And their best pitcher, John Tudor, starts Game 6. Dravecky was magnificent in their Game 2 meeting, but he's a 19-23 pitcher the past two years. Tudor's 23-9 in '86 and '87 on top of winning 20 of his last 21 in 1985.

If there is a Game 7, the Cardinals know who's pitching -- Cox, who looked sharp in his 4-2 complete-game loss in San Francisco. The Cardinals point out that Cox lost on two windblown homers that would have been outs in St. Louis.

Who starts a seventh game for the Giants? Reuschel's been hammered for 15 hits and eight runs in 10 innings. The Giants worry that his arm or his motion is out of whack. Atlee Hammaker? He was 2-8 on the road this year and has always gotten rattled away from home. "We can run on him," says Whitey Herzog. Did anyone mention Mike (Goofy) LaCoss (the Giants' leading winner), who called the team's traveling secretary during the Los Angeles quake to ask for a new hotel room because his was shaking? No, didn't think so.

Some senior Giants see the problem. Leonard was a grouch in victory Sunday. "Funny thing," he said. "Every time we've felt comfortable, we've lost."

The Cardinals, on the other hand, have a problem almost as great as the Giants'. To borrow Craig's phrase, their dobbers seem to be down. Maybe a season of foiling the Mets has exhausted them. Maybe the grind of trying to score without their Clark is taking its toll. St. Louis finished 31-31 as Clark was either pitched around or hurt.

Also, the NL East champions may be getting sick of waiting for Clark to mend. Since when does a sprained ankle take a month to heal? "They told me he'd be ready Friday," said Herzog. "I wonder what the hell Friday they're talking about. I've seen a lot of bad ankles, but never one like this." Clark has always been fragile and slow to heal. A sign in Candlestick, where Clark when he was a Giant was considered a moody star, said, "Jack Clark, the Giants' All-Time Sleep Leader."

Are the Cardinals more demoralized, or mad? They're sure hot about the Giants' showboating and popping off, but they're also embarrassed by the way the Giants have been the far more aggressive base runners. "They looked like the Gashouse Gang and we looked like a bunch of leadfoots," said Herzog, after Mathews absent-mindedly allowed two easy steals. "We couldn't have shot them down with a cannon."

"There's an awful lot of caution over there," said the Giants' Clark. "They usually steal early in the count. Now, they're going late, if at all."

The Cardinals have their home crowd, their experience, their annoyance with the Giants and their speedster pride on their side. Jack Clark might finally decide to tape up, limp and play. And having Tudor and Cox on line helps, too. But the Giants have Dravecky, who's never given up a run in 19 2/3 innings of postseason play. Obviously, the man likes pressure. And he's a master of exactly the sort of southpaw fastball-on-the-fists, then junk-'em-outside style that the Cardinals hate.

Right now, the Giants are happy campers. They got revenge on Bob Forsch, who'd stymied them Friday (and also hit Leonard with a purpose pitch). They heard the cheers that sophisticated San Francisco has seldom granted in the last 25 years. They finally got the prime-time exposure they coveted. Yet veteran Giants correctly sense the urgency of the moment. "Got to keep that intensity," said Krukow. "Forget Game 7. We're going out there Tuesday like it's the last game we ever played."

The Cardinals are down now, with double cause -- the Giants and their own injuries. But one game changes a lot in October. The Giants would be wise to focus on a quick knockout.