In the games of the postseason, every inning, every at-bat, every swing can be critical, the difference between landing a World Series berth and missing one. When two closely matched teams meet in the playoffs or World Series, the games are duels, blending strength and cunning, and the outcomes seem often to hinge on a single play.

In Cincinnati on Thursday night, and again on Friday afternoon, the Reds and Pirates, each vying for their first National League pennant in more than a decade, played tingly, alert baseball. In each game, one play became a modest part of baseball history.In the first game of the series, which resumes Monday afternoon in Pittsburgh, the Bucs defeated the Reds, 4-3, and the turning point came when Eric Davis, the Reds' brilliant outfielder, misjudged a two-out, seventh-inning fly ball with the game tied, 3-3, and runners on first and second. The Pirates' winning run scored on the play.

In the second game - which the Reds won, 2-1 - the final result rested on a throw by rightfielder Paul O'Neill. The throw, which caught Andy Van Slyke trying to advance to third, ended a sixth-inning rally for the Pirates. Never again did they have a runner in scoring position.

You know the plays were big, because you remember them so clearly in your mind's eye.

In the first game, Davis - the 1987, 1988 and 1989 Gold Glove centerfielder who was moved to left in mid-August to reduce the demands on his sore right knee - backpedaled clumsily on a deep shot by Van Slyke. Davis, the smoothest of outfielders, shot his big glove into the air, awkwardly. And then the ball bounced once on the plastic warning track and hopped over the fence for a ground-rule double. Gary Redus trotted in from second - no need to sprint - with the game-winner.

Davis has won scores of games for the Reds, with his bat and his speed and his glove. But that miscue cost his team a playoff game, and it will be better remembered than any tie-breaking, late-inning homer in May. The only thing those springtime game-winners do is get your team into the playoffs.

After Thursday's game, dozens of interrogators gathered around Davis, asking, "What happened? What happened? What happened?"

"I just misjudged it, that's all," Davis said. "I didn't think he hit it that good. It looked like he inside-outed it a little bit, but he hit it harder than I thought he did. After a couple of steps, when I turned and looked, I knew I was in trouble. I messed it up. That's all."

Todd Benzinger, the Reds' backup first baseman, who is writing a daily newspaper column for the Cincinnati Post during the playoffs, wrote the next day, "It was a hard catch. If I was out in left field, I probably wouldn't have caught it, but Eric's a Gold Glove fielder. He's our leader. When the ball's hit to him, we all expect him to catch it. It's probably a little unfair to put all that pressure on him, but he's a superstar, and that's what superstars are obligated to do. They've got to carry teams."

On Friday afternoon, it was O'Neill's turn. The Pirates, trailing by a run, opened the sixth with consecutive singles. Barry Bonds followed by lifting a fly to fairly deep right. O'Neill took a few steps toward the right-field line, about two steps deeper than where the ball would come down, angling his body so that it was perpendicular to third base.

Van Slyke, a few steps off the bag at second, watched the ball over his shoulder, his neck twisted. He ran back to the base, positioning himself to take off when Bonds' ball and O'Neill's glove met. Then he took off, shoulders low and thrusting.

O'Neill, a pitcher in high school, took two steps and heaved the ball. It went whizzing, low and sharp, over second base, then took a bounce and picked up speed. Third baseman Chris Sabo, straddling the bag, caught it, umpire Jerry Crawford thrust a clenched right fist into a cloud of dirt, signaling the out, and O'Neill raised a clenched left fist, signaling the victory.

"In every ball game you get at least one chance to win," Reds outfielder Herm Winningham said later. "The sixth was their time. Paul's throw was the turning point."

Later, O'Neill had to try to explain the throw, as if such an athletically stunning achievement can be set to words by its creator. (It can't.) Pirates manager Jim Leyland was asked if the Pirates were too aggressive on the base paths. (No.) Van Slyke was asked if he would attempt the tag-up again. (Yes.) manager Lou Piniella was asked if it changed the outcome of the game. (Yes.) Shortstop Barry Larkin was asked if he considered cutting off the throw. (No.)

"Those plays happen so quickly, you can't describe how you did them," O'Neill said. He could have been talking about Davis' blunder. He could have been talking about Kirk Gibson's ninth-inning, two-out home run in Game 1 of the 1988 World Series, which gave the Dodgers a 5-4 win over the A's. He could have been talking about Willie Mays' tie-preserving, eighth-inning over-the-shoulder catch off a Vic Wertz drive in the first game of the 1954 Giants-Indians World Series. He could have been talking about any important baseball moment that happens in a flash and provides conversation for days, weeks, sometimes even years.