The question was simple enough: Why put 19-year-old Bryce Harper, the youngest player in the major leagues, in the No. 3 spot in the lineup already, only five games into his career with the Washington Nationals?

Manager Davey Johnson's answer, delivered with as straight a face as can be, was simple, too: "Why not?"

"I mean, he's swinging the bat good. He's had quality at-bats. It's what you do. I don't care if his name's Harper or whatever. Or how old he is," Johnson said before Washington hosted the Arizona Diamondbacks on Thursday night. "He looks like a pretty good choice to me."

Well, that sure didn't take long.

Harper is an outfielder who's been hitting seventh since being called up from Triple-A Syracuse on Saturday. He joined the Nationals to fill the roster spot vacated by usual No. 3 hitter Ryan Zimmerman, the third baseman who went on the 15-day disabled list.

Asked about his new slot in the batting order before Thursday's debut at No. 3 against Diamondbacks pitcher Ian Kennedy, Harper replied: "Am I hitting third? Oh, I didn't see that. Oh, great. Cool. I have no words for that. Just hopefully I can make something happen and get us going."

Nothing, it seems, rattles the confident kid, who entered Thursday with a .385 average, three doubles and two RBIs.

He went 3 for 4 in Washington's 5-4 victory over Arizona on Wednesday night, including a leadoff double off the wall in the ninth inning. He wound up scoring on Ian Desmond's game-ending two-run homer with two outs.

Could hitting third be daunting to a teenager still with less than a week's experience in the majors?

"I think for A guy that young, but not THAT guy that young. You know what I mean?" Desmond said. "He's going to be a 3-hole hitter or a 4-hole hitter. He's going to hit for power. He has a good eye. He's aggressive. He thrives in those at-bats. It's a good test. I think it's a good test. We're going to see what he's got."

The last time a younger player started in the third slot in a major league lineup was 1996 when Andruw Jones did it for Atlanta, STATS LLC said. B.J. Upton was 19 but older than Harper when he hit third for Tampa Bay in 2004.

Plus, as Johnson noted, there aren't a lot of other options for the Nationals at this point.

The Nationals got off to a 15-9 start, best in the NL East, despite having a lot of trouble scoring runs. Before Wednesday's comeback win, Washington had scored a total of seven runs in its previous five games, all losses.

"We're trying to find our way a little bit," Johnson said about his team's offense.

It doesn't help that Johnson can't use Zimmerman or Michael Morse, the injured slugger who was supposed to be the cleanup hitter. Plus, a couple of hours after Harper already was written in to bat third Thursday, fill-in cleanup hitter Adam LaRoche was scratched because of a sore right side muscle.

The Nationals bumped Jayson Werth up from fifth to fourth. Chad Tracy took over for LaRoche at first base, hitting fifth.

Harper was the No. 1 overall pick in the 2010 amateur draft after finishing high school early, then spending one season as a catcher at a junior college.

"He's an aggressive hitter. He's patient. He's all the things you look for in a hitter. He's trying to get a ball he can drive, every time he gets ready to take a swing. And if it's not in the zone, he'll take it. Very seldom, he'll swing at balls out of the strike zone," Johnson said. "When you're that aggressive and that talented, sometimes you'll fish a little bit. But by and large, he's handled himself like he's been here a while."


Howard Fendrich can be reached at http://twitter.com/HowardFendrich