But these things happen. So Kozma was recalled from Triple-A Memphis the next day and became the Cards' everyday shortstop down the stretch. He even started the final 16 games as St. Louis wrapped up a National League Wild Card playoff spot, and the team never missed a beat, winning 12 of them.
There was no real reason to suspect that, on a team with Matt Holliday and Carlos Beltran and Yadier Molina and David Freese, Kozma would find himself front and center once the postseason started, but that's exactly what has happened.
In Friday's NL Wild Card game win over Atlanta, Kozma first called for a pop fly hit by Braves shortstop Andrelton Simmons, then bailed at the last moment. The ball dropped between him and Matt Holliday in shallow left field, and the Braves -- down by three in the bottom of the eighth -- seemed to be in business with the bases loaded and one out.
That, of course, is when the umpires called Simmons out on the infield fly rule, igniting a firestorm and leading the Braves to play the game under protest.
Then on Sunday at Busch Stadium, the Cardinals led Game 1 of the NL Division Series by a run going into the eighth inning. St. Louis reliever Mitchell Boggs got Washington left fielder Michael Morse to hit a grounder to Kozma for what should have been the first out -- except that it bounced off the shortstop's glove for an error. That wouldn't have been a big deal except that the Nats went on to score two unearned runs to win, 3-2.
"I missed it," Kozma said. "I make that a hundred times, maybe miss it once. It's just one of those games."
He added that the ball didn't take a bad hop and that he didn't rush himself on the play. Kozma didn't second-guess himself for backhanding the ball instead of trying to get in front of it.
"I just thought it was hit hard enough for me to backhand it," he said. "It hit my glove."
Despite being pushed into the spotlight, Kozma said he's enjoyed his postseason experience so far.
"It's pretty good," Kozma said. "A bunch of the older guys have talked to me, just talked to everybody in general, just to kind of calm us down and help us do our thing."
He conceded that can be easier said than done.
"Of course, you never really know until you're actually in it," Kozma said. "It's still the same game, just a little bit more on the line, but you can't think of that. You have to think about the game. You've got to forget what's happened. It's in the past. Nothing you can do about it now. Learn from our mistakes and go on."
Kozma was the Cardinals' top pick in the 2007 First-Year Player Draft. He batted .333 in 26 games after being called up. And yet, in the last two games, fate has singled him out. That's the way it goes sometimes. How often does a defensive replacement get tested on a difficult play right after he goes into the game?
The Cardinals' only realistic option would be to move second baseman Daniel Descalso to shortstop and start Skip Schumaker at second. But manager Mike Matheny indicated after the game that he probably won't do that. He added that he didn't believe the bright lights of the postseason can test a player with as little big league experience as Kozma has.
"No, he's been very consistent for us," the manager said. "That was a tough play. The ball bounced up and got him pretty good. But I see him making very good plays. And just kind of watching him and what he's doing, he's ready for this."
Matheny isn't the only person eyeing Kozma these days, of course. It's the postseason, which means the world is watching.
Paul Hagen is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.