(Jeff Roberson/AP)

Bryce Harper has only 10 more days left as a teenager, before his 20th birthday arrives Oct. 16.  Of course, he has not behaved like one all season, and his unflappable maturity didn’t go anywhere with the arrival of his first postseason.

As Harper stood in the Nationals’ clubhouse following their workout at Busch Stadium, he seemed almost confused at the questions about how he would keep himself calm for his first playoff game. Nervous? Not when it comes to baseball, not for Bryce Harper.

“I think you guys are more nervous than we are,” Harper told a group of reporters. “It’s just another game. It’s another series. I’m excited, but I’m just going to look at like it’s another game, another place that we play, another team we play. I guess when you step in box, it’s going to be a lot different with the crowd and everything. But you can’t look at it that way.”

Harper was asked specifically about the moment players are introduced, lined up on the baselines before a packed, frothing crowd. He paid it no mind. Harper sported a new hair color — “deep black,” he said — but otherwise, for him, the playoffs meant no new approach.

“If they called your guys’ name, you might be a lot more nervous than I am,” Harper said. “You just try to go out there and play the game you know how to play. You’re not worried about everything around you. Clear everything out, and have some fun while you’re doing it. If you have fun and play the game you’ve been playing your whole life, that’s what matters.”

Harper had success playing his game against the Cardinals this year. In 31 at-bats against St. Louis, Harper punched up a 1.234 OPS with two home runs. Against the starters slated to pitch for St. Louis, he went 7 for 14 with two doubles, a homer and a walk.

No stage has been too big for Harper this season. Given his demeanor today and his success against the Cardinals, the postseason will not be any match for him, either.