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At least 45 minutes after he walked across the diamond to high-five Adam LaRoche and celebrate the first playoff victory in his team’s first playoff game, Nationals third baseman Ryan Zimmerman stood in front of his locker in Busch Stadium’s visiting clubhouse and marveled at the experience. He has friends and former teammates who have endured what took place Monday afternoon in the Nationals’ enthralling 3-2 victory over the St. Louis Cardinals in Game 1 of their National League Division Series. But now that he has been through it himself, he has a different sense of what playoff baseball is about.

His conclusion: This is a mixture of fun and exhaustion that can’t be duplicated.

“It’s just a different focus,” Zimmerman said. “It’s just more mentally – not so much during the game. When you’re down on the field, or when you’re at bat, it’s the same. But in between innings, you’re watching everything. You’re talking with everyone. Everything. You bear down.

“And if you lose, it’s huge. It’s not that losing in the regular season is not a big deal, but it’s exhausting. That’s the best word to describe it.”

Zimmerman, the Nationals’ longest-tenured big league player, appeared in 990 major league games and had 4,310 plate appearances before his postseason debut. In describing the experience – with another game on tap Monday, with the same roller coaster getting ready to depart – he tried to walk difficult line. The regular season, he said, has its own intensity in which every game and every at-bat are important. Don’t dismiss that, he said. But this is different.

“I think the last two-and-a-half weeks of the season, we were playing guys that were in the pennant race or trying to win a division or trying to make the playoffs,” Zimmerman said. “It’s not easy to close out a division, either, when you’re trying to close out those guys. We’ve kind of been in these games for the last two-and-a-half weeks.

“I think that kind of helped us, honestly, instead of just playing teams that were out of it or playing teams that are playing kind of some young guys to see if they can be someone. … So it kind of got us ready – almost ready. But I don’t think you can kind of prepare for something like this unless you’ve been in it a few times. I know a bunch of us were talking how much fun it was and how exciting it was. It’s what you work hard for, to get to this point.”

Now,  about that throw. In the eighth inning of a game the Nats led by one run, Zimmerman cleanly fielded David Freese’s leadoff grounder. But in what has become an uncomfortable sight for Washington fans, he hesitated on the throw, then skipped it in the dirt. LaRoche, the first baseman, couldn’t dig it out, and Freese reached on Zimmerman’s first postseason error.

“Just a bad throw,” Zimmerman said. “I felt great. I just messed it up.”

Zimmerman has insisted that his ailing right shoulder, in which he has received two cortisone shots this season, has not affected his throwing. But his error put the tying run on first, and Freese advanced to second on Daniel Descalso’s sacrifice bunt. Setup man Tyler Clippard was, in essence, forced to get four outs in the inning, but he got Zimmerman off the hook by getting Pete Kozma to pop up to first and then striking out pinch hitter Matt Carpenter.

“I’ll be fine with it,” Zimmerman said.