A popup that dropped in shallow left field.
The call, by veteran umpire Sam Holbrook, put the damper on a would-be Atlanta rally in the eighth and triggered a 19-minute delay as irate Braves fans littered the field, throwing water bottles, paper cups and anything else they could find. Players ran for cover as the grounds crew removed the debris.
Toss in a crucial fourth-inning throwing error by Braves All-Star third baseman Chipper Jones in his final game, a baserunning interference call that went against Atlanta and you have a vivid snapshot of how this contest went.
And why most in the sellout crowd of 52,631 found the outcome difficult to accept.
The Cards, who have a knack for finding ways to win these important games, go home to play Washington in the National League Division Series, which begins Sunday at 3 p.m. ET on TBS.
But it will be what I think was a blown call, or at best a stretch of the infield fly rule, that will linger.
Jones, a certain future Hall of Famer, disagreed, after saying he cost his teammates the game when he threw wildly into right field on a certain double-play ball in the fourth inning that paved the way for three St. Louis runs.
"Ultimately, I think that when we look back on this loss, we need to look ourselves in the mirror," Jones said. "We put ourselves in that predicament, down [6-3] at the time.
"You know, that call is kind of a gray area. I don't know. But I'm not willing to say that that particular call cost us the game. Three errors cost us the ballgame, mine probably being the biggest."
Jones was correct when he said the infield fly ruling is a gray area.
With the Braves down, 6-3, runners on first and second with one out, shortstop Andrelton Simmons lofted a high fly ball to shallow left field -- about 90 feet from the infield dirt.
Cardinals shortstop Pete Kozma ran to the outfield grass for the ball, then stopped when left fielder Matt Holliday charged in. The ball dropped between the two fielders.
It appeared the Braves would have the bases loaded, but Holbrook would say later he immediately called the batter out, using the infield fly rule. Immediately after, third-base umpire Jeff Nelson also signaled out.
When Simmons was called out and Braves manager Fredi Gonzalez raced onto the field to argue, the crowd erupted.
In a bizarre series of events, the Braves protested the game, MLB executive vice president of baseball operations Joe Torre, in attendance, rejected the complaint in real time, and after the field was cleaned, the game resumed.
There has been widespread debate about the fairness of a one-game playoff between the two Wild Card teams in each league, and for the first one to end as it did Friday night fuels that fire.
Torre, in his capacity as head of baseball operations, oversees Major League umpires. He said after the game, in his opinion, it was an infield fly, "but again, it's a judgment."
Holbrook said, "I saw the shortstop go back and get underneath the ball where he would have had an ordinary effort and would have caught the baseball. That's why I called the infield fly."
Gonzalez said, "I was arguing or protesting that it was not an ordinary effort. I thought the shortstop had to go way out there to make the play on that fly ball, and I think we've got to take into account the crowd of 50,000 people yelling. I thought there was some miscommunication between Matt Holliday and Kozma."
Cards manager Mike Matheny said there was no doubt.
"We saw what happened," he said. "We saw the infield fly [rule] being called. Guys in the dugout yelling and pointing. So I understand why the Braves would be frustrated. We get that. When that call is made, a couple of things can happen: We know the ball is dead, runner is out and runners advance at their own risk."
There was an obvious miscommunication between Holliday and Kozma, and yes, the crowd probably played a role. They seemed uncertain who was actually calling for the ball.
But in 54 years of covering Major League Baseball, I've never seen the fly rule called when a fielder isn't under the ball. The infield fly is a complicated rule, designed to prevent infielders from intentionally dropping a popup with more than one runner on base to perhaps get an extra out.
It wasn't even close in this case. As Holliday charged in, Kozma, his glove outstretched, took a few steps back, deeper into the outfield.
For the postseason, MLB uses six umpires. Normally, if such a call were to be made, it would be handled by the third-base ump. Holbrook was the left-field umpire Friday night.
Holbrook said, after later reviewing the replay, "There was absolutely no second guess" of the decision.
The Braves have spent this entire season trying to put behind their 2011 season, when they collapsed in September and watched the Cardinals win the NL Wild Card; there was just one in each league before this new format was concocted.
Now, Atlanta will have to spend another long winter wondering what might have been had it not been for three early errors and an eighth-inning call that defined the first game in this win-or-else round.