He hadn't yet met the 19-year-old with the rattail haircut, but Upton and Bryce Harper certainly knew who each other was.
The mutual recognition goes well beyond the casual international encounter. As the Harper Era begins -- the Nationals' prodigy played his first major league game on Saturday -- no one has a better understanding of Harper's situation than Upton who, by chance, was his opponent on Tuesday for his home debut at Nationals Park when he went 0-for-3 in a 5-1 loss.
Both, after all, are No. 1 overall draft picks and five-tool prospects who played a different position in high school before moving to the outfield in the minor leagues and then making their major league debuts at 19 as injury replacements.
"I wish I had known to relax and just play the game," Upton said of his rookie year. "I'm happy for him. To be in the big leagues at this age, it can be fun if you let yourself have fun."
Harper said he felt comfortable this weekend in Los Angeles, where he showed all five tools in just two games against the Dodgers by demonstrating great strike-zone awareness in taking a walk on close pitches, smacking a double off the fence, nearly beating out an infield single, unleashing a terrific throw home that beat the runner and crashing into the outfield wall to make a leaping catch.
"I'm trying to stay as calm as I can," he said. "Take one at-bat at a time. One pitch at a time. And make things happen, I hope. I'm just going to come out here every day and give 110 percent and play hard and try to walk away with a W."
Many of Harper's answers on Tuesday may have been full of clichés, but he knows humility plays better than brashness when you're a rookie of whom so much is expected. Harper is the latest teenager to debut in the last 25 years, joining an illustrious group that includes Ken Griffey Jr., Alex Rodriguez, Andruw Jones, Adrian Beltre, Gary Sheffield and the Upton brothers, Justin and B.J. But the track records in their debut seasons aren't great -- no teenager in the last quarter-century has had double-digit at-bats and an OPS of at least .760.
No one, however, knows quite what Harper's life is like in the modern world of media and hype. An SI cover boy at age 16, he's been in the national spotlight for years.
To wit: Never having seen the Lincoln Memorial before, Harper went sightseeing on his off-day in D.C. While passing a slow-pitch softball game on the Washington Mall, he was asked to pinch-hit -- and he did, with the footage swiftly hitting the Internet.
For the most part Harper has joined the Nationals under the best circumstances -- a promotion predicated by injuries to a big-league club in first place in the NL East. There's no guarantee that the prodigy remains in the majors for good; if he is returned to Triple A, well, that was just part of the plan all along, alleviating pressure on him to excel immediately.
"I don't think I have to prove anything," Harper said. "I'm trying to stay up here as long as I can and play as hard as I can every single day."
Said Nationals general manager Mike Rizzo, "If he's ready mentally, physically and emotionally to stay here, then he'll stay. He may change the developmental plan for us."
Given the personnel and record of the team Harper has joined, he doesn't need to be a savior. That much was apparent in the small (though spirited) crowd of just 22,675, barely half the more than 40,000 fans of the sellout that witnessed Stephen Strasburg's debut two years ago.
Harper, who struck out and grounded out twice, did receive a standing ovation for his first at-bat and again for a 290-foot, sixth-inning straight-line throw home from deep leftfield that narrowly missed getting the runner at the plate on a sacrifice fly.
No matter the expectations for Harper in 2012, the reality is that Washington could use a jolt. Its lineup -- depleted without Ryan Zimmerman and Michael Morse, both of whom are on the disabled list -- has scored just seven runs in its current five-game losing streak. Its left fielders were batting .097 at the time he got his call.
"He belongs here right now," manager Davey Johnson said. "He fits. He gives us a little more left-handed presence in the lineup, which we've been looking for.
"The only thing that I've been thinking about, really, is how long I hit him seventh."
Harper was only hitting .250 with one home run and a .333 on-base percentage in 20 games at Triple A but had gone 9-for-31 (.290) in his last 10 games. But he also admitted that he may have been pressing in order to hurry his big-league promotion.
"In Triple A, it was like, 'I've got to prove, I've got to do stuff to get back up to the big leagues,'" he said. "I wanted to be there so bad. Once I got up here, it was like a calm went over my body. You're here. Just play your game like you know how to play."
Johnson, who managed the 1980s Mets with youthful stars Doc Gooden and Darryl Strawberry, said Strawberry was an example of a hitter who played better after reaching the majors.
"I do think the driving force of getting to the big leagues puts more pressure on you at that level, trying to do too much," Johnson said. "And that's the one thing, to be a good hitter, you have to stay within yourself."
There are players in Harper's own clubhouse who can appreciate at least some of his experience. Third baseman Ryan Zimmerman was drafted as a 20-year-old in June 2005 and debuted that same September. Starter Stephen Strasburg was a fellow No. 1 overall pick whose big-league debut was, Rizzo said, the second most hyped game he had ever been apart of, trailing only World Series Game 7 in 2001.
And starter Edwin Jackson also changed positions in the minors -- from outfield to pitching -- and was called up at 19 years old before making his debut in a start against Randy Johnson on his 20th birthday.
"I'm sure he has more pressure than I had," Jackson said. "He's been on the clock since he signed. Media nowadays is different from it was back then."
The best comparison remains Upton, who joined a first-place Diamondbacks club for a 43-game call-up in 2007. He started slowly -- hitting .221 with two homers -- but the team was playoff-bound anyway. And Upton batted .357 (5-for-14) in the postseason as Arizona reached the NLCS.
Rizzo was the Diamondbacks' scouting director when Upton was drafted and the Nationals' G.M. when Harper was drafted.
"Some guys have the propensity to take it to the next level anywhere they play, and I think he's one of them," Rizzo said, referring to Harper. "The only person that I've had in my career that mirrors him a little bit is Justin Upton. Those are the two elite position players that I've had."
Upton was a 20-20 player and All-Star by 2009, when he played most of that season as a 21-year-old, and a fourth-place finisher for NL MVP as a 23-year-old in 2011.
The expectations on Harper are even higher. For now, the Nationals will be plenty happy with Harper just being a contributor. Stardom will come.