Correction: An earlier version of this column incorrectly said that Willie Mays was 19 when he first played major league baseball. He was 20. This version has been corrected.

When Willie Mays hit the big leagues at 20, he couldn’t get the little kid out of himself, didn’t want to anyway and used to play stickball on the New York streets. On Monday, on his first full day in Washington as a big leaguer, Bryce Harper, 19, visited the Lincoln Memorial, then stopped on the Mall near the Washington Monument. That’s where they have the public softball fields. Day off, new town, what are you going to do?

You might think a teenager in blue jeans and a ballcap might go unnoticed but, as Harper admitted: “They see the rat tail and the tattoos. I think they can notice that.”

So the Nationals’ already famous rookie, who made his home debut on Tuesday night, going 0 for 3 in a 5-1 loss, was asked to take a few swings in the casual pickup game.

“Nah, I don’t know about that,” he said, but then quickly relented. The results of his two friendly, but hard swings: “I just knocked one into right field.”

Actually, Harper swung at the first super-slow softball pitch and missed. Missed! Trying too hard to please? Or is he just such a quick-twitch freak of an athlete that 20 mph isn’t his hitting speed? Seven-time batting champion Rod Carew hated slow-pitch softball, too, looking foolish. Pitchers joked that they should toss the ball up underhand.

That’s where Harper is now: between possibilities. Within weeks he could be establishing himself in the major leagues permanently, or he could be back in Class AAA, where the Nats’ “developmental plan” projected him for much of this year.

In fairly short order, he could be on the way to true stardom in one to three years with comparisons to household names that stuck in the big time at 19 and emerged full-blown at 20 or 21 as elite players.

On Tuesday, Harper put on a batting practice show that begged for comparisons. Had Manager Davey Johnson ever seen a hitter swing so hard in BP, crushing homers to all fields, while maintaining balance and mechanics? “Mantle,” Johnson said.

Though he was bedeviled by Trevor Cahill’s change-ups all night, swinging and missing five times (three on changes), Harper also managed two hard infield smashes along with a strikeout in his 0 for 3.

In the field, he made a nice running catch that the Nats’ slower left fielders might not have reached and unleashed two more amazingly strong and accurate throws, proving, within four days of his arrival, that he’s one of the few rivals in MLB to the Nats’ Rick Ankiel for best outfield arm. He came within a foot of throwing out quick John McDonald at the plate on a 100-yard on-the-fly peg that made the crowd of 22,675 gasp.

“Everybody was yelling and screaming . . . I got the chills out in left field,” Harper said of his early introduction, adding of his groundout smash up the middle, “I was pretty upset. I hit it between [Cahill’s] legs up the gut and they got me” at first.

Despite his two strong games in Los Angeles, every question is still on the table concerning Harper — at least as a 19-year-old. Perhaps Harper has a secret vulnerability like that goofy softball swing and miss. Maybe he’s been brought to the majors too quickly, an emergency shot of adrenaline for a sickly Nats’ offense that looks hopeless without Michael Morse and (until Sunday at the earliest) Ryan Zimmerman.

The entire Nationals organization, with the exception of General Manager Mike Rizzo, who’s perhaps the sanest of the crew, thinks Harper belongs in the majors now, that he should be given an incredibly long leash and that his obvious five-tool skills can help the team in so many ways that any one stat, such as batting average, is an illusion.

Besides, they want this guy tested in the fires as soon as possible because they want him in the 2013 Opening Day lineup — and with more than minimal call-up experience this September — when they intend to be a playoff team, with young Harper one key factor.

“I don’t know why anyone is worried about him. Age is just a number. He’s got that special ‘it’ factor,” Zimmerman said.

For the moment, the Nats’ operative assumption is that Harper is an example of a rare breed — the player destined from an early age, either by bloodlines or talent — to be a standout major leaguer. That, they think, makes the big leagues a better, easier and more appropriate place for him to gain experience than AAA.

Adam LaRoche’s father was a big-league pitcher. The Nats’ first baseman remembers: “I was expecting to be a big leaguer my whole life. From T-ball on up, I never had a doubt I’d play in the league. All the pressure is working your way up through the minors.

“That’s exactly how Harper feels. This is the way he always expected it to be. He’s ready. He’s been ready forever. When he got to Los Angeles, he [told me] he had not felt so relaxed for any game since he became a professional.”

Harper was surprised and a bit confused by his own time-slows-down reaction to a debut before 54,000 people in Dodger Stadium. “I got really calm as soon as I got to L.A.,” he said. “In AAA, it’s like I gotta prove because I wanna get up there so bad. Now, I’m here. Stay in the moment.”

“Young players with a lot of potential — their goal is the big leagues. They want to hit .600 or hit a 500-foot home run,” Johnson said. “They try to do too much.”

And they only play within themselves, use their skills properly, when they’ve gotten to the level which, at a deep lifelong level, they think they belong.

“He may change our development plan,” Rizzo said. “In his mind it’s probably, ‘Why is this guy so dumb that he didn’t bring me up sooner?’ ”

“I’m just going to come in here every day with open eyes and open ears,” Harper said.

That will probably be enough. Now that Harper is here, the Nationals should give him absolutely every benefit of the doubt to stay in the big leagues until Morse comes back — around the all-star break, at the earliest. Then make a decision if necessary.

But until then, unless he is absolutely overmatched night after night, leave him alone. He’s likely to develop better and faster against the best competition — and, considering his sharp batting eye, with the best umpires. This is where Harper belongs — unless he proves otherwise.

Which is unlikely.

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