Pete Kozma, shown in action over the weekend in Philadelphia, broke plenty of Nationals fans’ hearts during last year’s NLDS. (Matt Slocum/AP)

Life in St. Louis, for Pete Kozma, is uncertain. His position as the Cardinals’ starting shortstop seems perpetually tenuous, even as his name appears in the lineup day after day. He is chastised for who he isn’t rather than embraced for who he is, criticized for what he hasn’t done rather than praised for what he has.

“I know people want to keep throwing his minor league record in his face all the time,” said Mike Matheny, the man who manages him.

“Cardinal Nation vilified him,” said Jeff Luhnow, the man who drafted him.

In Washington, Kozma’s standing is undeniable. It is here where he has been truly vilified, where months ago he began — then became the symbol of — an angst-filled winter. In St. Louis, his future may be undetermined, because he is technically filling in for an injured veteran. Matheny said of Kozma’s job even last week, “He walks in here every day realizing that he’s got to 1, earn it, and 2, keep it.”

But in Washington, Kozma is forever a villain. Boston has Bucky Dent. Pittsburgh has Francisco Cabrera. Philadelphia has Joe Carter. And as of last Oct. 12, Washington has Pete Kozma.

The Post Sports Live crew discusses whether the Nationals bullpen woes, Ryan Zimmerman’s throwing errors and Wilson Ramos’s injury are reasons to worry. (Post Sports Live)

“I remember the feeling,” Kozma said. “There’s nothing like it.”

It is the feeling of silencing a ballpark, of ending a season. Monday, Kozma and the Cardinals make their first visit to Nationals Park since the decisiveGame 5 of the National League Division Series. That night, they finished off the Nationals in a manner that scars players and teams and fan bases. They came back from an early six-run deficit, back from a two-run deficit in the ninth. They faced five pitches that could have been their last strike.

For many, Kozma, 25, is the player who personifies the Nationals’ collapse because he faced three of those two-strike pitches, and delivered the two-run single that soon gave the Cardinals an astonishing 9-7 victory.

But that picture of Kozma is incomplete.

“After everything he went through, another player would have succumbed,” Luhnow said. “And he didn’t.”

Who’s Pete Kozma?

Luhnow is now the general manager of the Houston Astros. But in the spring of 2007, he was the vice president of scouting and player development for the Cardinals. That June, St. Louis had the 18th pick in the draft. When their turn came up, Rick Porcello, a high school right-hander from New Jersey, remained available. At that moment, at his parents’ house in Owasso, Okla., Kozma had finished taking some hacks in the batting cage. His parents had invited a few friends over to watch the draft. Pete hadn’t bothered.

“I didn’t think there was a chance I’d be taken in the first round,” Kozma said. “I had no idea.”

Everyone in baseball knew of Porcello, because his adviser was Scott Boras, who doesn’t shy away from making historic demands for his players, which gets some teams to shy away from him. Porcello was, by consensus, a top-five talent in that draft. Kozma was not.

“We had Rick Porcello high, as everyone did, but we had concerns, like a lot of other teams did,” Luhnow said. “Pete was the best player on our board. We felt great about taking him. But the poor guy. . . . [The reaction] had nothing to do with him. It had to do with the fact that he wasn’t Rick Porcello.”

Cardinals fans were left with a direct-but-unfair comparison: Why did we take this guy when we could have had Porcello? Detroit took Porcello with the 27th pick and signed him to an $11.1 million deal that was then a record for a high schooler. By 2009, Porcello won 14 games for the Tigers. Kozma’s batting averages in his first three minor league seasons: .233, .258 and .231. Being a first-rounder, it turns out, could be a burden.

“You’re trying to go out there and get five or six hits a game,” Kozma said. “I felt like if I didn’t do that, I didn’t do anything that day.”

Internally, though, the Cardinals were comfortable with his development, even if the production appeared substandard. Luhnow said Kozma’s minor league managers always wanted him back, always wanted him in the lineup.

“He was younger, still learning a lot of stuff,” said Cardinals second baseman Daniel Descalso, who spent much of 2009 with Kozma in Class AA. “He was a high school kid, so it might just take a little longer. But it seemed like every year, he improved.”

In 2011, Kozma got a taste — 16 games in the majors because St. Louis infielders Nick Punto and Skip Schumaker went down with injuries. “I just watched,” he said, “and took away things I needed to improve on.” And on Aug. 30 of last season, when only four games remained for Class AAA Memphis — where Kozma had split time as a second baseman and shortstop, hitting all of .232 — Cardinals shortstop Rafael Furcal suffered a ligament injury in his right elbow against the Nationals. Kozma’s phone rang that night. He ended up on a flight to Washington. He was in the lineup the next day.

“I just tried to apply everything I’d learned,” Kozma said. “I felt good in Memphis, even though my numbers didn’t show it. I felt like I was making solid, consistent contact, putting the ball in play. But not everyone sees that. We’re in the cage, taking BP, practicing all these hours, taking all these groundballs, and when your numbers aren’t showing it, it sucks.”

Unexpected production

Matheny tried to mix Kozma in with Descalso and Schumaker in the middle infield. Then the unexpected happened: Kozma produced. By mid-September, he was the shortstop. As the Cardinals pushed to the playoffs, he started the final 16 games and hit .333 with a .952 on-base-plus-slugging percentage. His highest OPS in any minor league season: .702.

Still, when he came to the plate in the ninth inning of Game 5 against the Nationals, he had just three hits in 19 postseason at-bats. David Freese stood on third, Descalso on first, the score tied at 7. Cardinals closer Jason Motte stood in the on-deck circle, Drew Storen on the mound.

“I didn’t think they were going to pitch to me,” Kozma said. “It was in the back of my mind. I was just like, ‘Be patient. Get your pitch.’ ”

Storen pumped in two fastballs for strikes. “All right,” Kozma thought. “They’re going to pitch to me.” Storen missed with a fastball, a pitch on which Descalso stole second. Kozma then took a slider for a ball. At 2-2, Storen came back with a fastball on the outer half of the plate, “a really good pitch,” Kozma said. He went with it and sent it to right to drive home both runners. Storen went on to retire Motte, who in the bottom of the inning retired the Nationals in order. Washington’s season was over.

Kozma said he asked the Cardinals’ video staff for a DVD of the game, but he hasn’t yet watched it. And again, the play meant more for Kozma’s standing in Washington than it did in St. Louis. With Furcal’s health still in question as spring training approached, the Cardinals signed veteran infielder Ronny Cedeno, a move that could have been an affront to Kozma.

“I think a few of us took it personally,” Kozma said. His response: Hit .359 in spring training. With Furcal still injured, Cedeno was released, and Kozma won the job.

“He looked exactly like the guy that left us in October, the same guy that showed up in September,” Matheny said. “We just keep telling him that that’s the only guy we know, so keep being him.”

Being Pete Kozma means different things in St. Louis and Washington. Thursday afternoon at Citizens Bank Park, he checked the heavy-stock paper taped to the wall, that night’s lineup against the Phillies, for his name. And there it was, again.

He will not, he said, take a moment to reflect on his moment before Monday’s game at Nationals Park. He will, almost certainly, be booed upon his introduction, upon his first at-bat. Whatever he does in St. Louis — whether he goes on to be an all-star or an also-ran — his place in Nationals history is secure, always the antagonist.