Now just 19, the 6-foot-3, 215-pound Harper is a player people can't stop watching. That comes with the territory of being a true phenom.
Instead of being swallowed by the suffocating expectations, Harper is having a blast.
"I am way more comfortable here than in the minor leagues," Harper said after going 0-for-4 with a walk in Saturday's 7-1 win over the Phillies at Nationals Park. "I feel like in the minors I was trying to prove and prove and prove I belonged in the big leagues."
After he was selected with the first overall pick in the 2010 Major League Baseball First Year Player Draft, many observers predicted it would take Harper less than two years to reach the big leagues.
Being taken first doesn't guarantee instant success. For instance, the 2008 No. 1 pick, Tim Beckham of Tampa Bay, recently was suspended a second time for violating the minor league drug program. Just in the last decade, players such as Matt Bush and Bryan Bullington were considered No. 1 overall washouts.
Harper falls in the category of Ken Griffey Jr. or Alex Rodriguez in terms of hype and expectation. Whether Harper ever rises to the level of Griffey or ARod remains to be seen.
It should be fun to watch, though.
Harper earned his promotion when current franchise cornerstone Ryan Zimmerman was placed on the 15-day disabled list, retroactive to April 21 due to shoulder inflammation.
"He's pretty good," Zimmerman said of Harper.
Then the Nationals third baseman expanded on those comments.
"The best thing we all noticed here when he gets in those big situations, you can kind of tell who has it and who doesn't, and he stays calm," Zimmerman said.
It seems as if opponents are buying into the hype. In the Nationals' first two wins in this three-game series, Harper was walked four times.
"He's getting a lot of respect for only being here a couple of days," Nationals manager Davey Jonson said. "They are pitching him tough, even behind in the count they are throwing him a lot of off-speed stuff."
On Friday, Phillies starter Kyle Kendrick walked Harper twice. Kendrick was asked if he pitched around him. He said no, but then basically said he did.
"Not really, but I wasn't going to let him beat me," Kendrick said. "He's swinging it well now; that was the scouting report."
Harper's teammates have noticed his plate discipline.
"He's up there hacking so for him to get in good counts and seeing pitches, it's good and shows his patience at the plate," said Jayson Werth, who blasted a three-run home run in Saturday's win.
Harper admits that taking pitches goes against his aggressive style.
"It's going to be a little bit of a challenge to be patient and wait for my pitch, to try to stay within myself and not chase their pitches," Harper said. "The past two games against Philly I had four walks and I'm trying to contribute every way I can, and we got two W's so that is all that counts."
Harper made his major league debut in a 4-3 loss in 10 innings at Los Angeles against the Dodgers on April 28 before a sellout crowd of 54,242.
He is not only winning over fans, but his teammates as well. The Nationals receive a steady flow of media requests whether at home or on the road for Harper. While this might cause some jealousy, it's had the opposite effect, according to first baseman Adam LaRoche.
"No, it takes the media members away from everybody else," LaRoches said. "It puts it all on one guy and let him enjoy it for a while, but you aren't going to see any jealousy from any of these guys."
And there is one simple reason.
"If a guy is playing 110 percent like he does and will help us win games, we welcome him," LaRoche said.
Zimmerman said before Saturday's game that he should be returning soon. There was speculation in the media that when Zimmerman returns from the disabled list, Harper will be sent back to the minors.
"Everybody assumed that would be the logical move, but we never put that in stone," Nationals general manager Mike Rizzo said.
What is set in stone is that Harper, who has already been elevated to the No. 3 spot in the batting order, isn't changing his address anytime soon.
"He's playing well enough to stay in the big leagues for sure," Rizzo said. "He gives us an impactful bat in the middle of the lineup, and it certainly won't be in the near future we will send him back."
And thus the phenom watch will continue at the major league level, something that will continue to draw plenty of interest.
Contact Marc Narducci at 856,779-3225, firstname.lastname@example.org or @sjnard on Twitter.
Inquirer writer Matt Gelb contributed to this article.