For starters, there's the ol' human element to consider, that nobody can be at his best at all times, even if the Nationals' über-prospect is at that high level more often than possibly any other 19-year-old.
There's the simple reality that he isn't just a novelty act looking to showcase his 80-grade power -- the scouting scale's max -- with every swing of the bat.
He is, after all, a minor leaguer who hasn't played above Double A ball and who needs to impress upon Washington's coaches and executives that he's ready to make his first major league club.
"I'm going to come in here and force their hand and try to make the decision as hard as I can," Harper said recently. "I'm trying to have an open ear to everything everybody says."
Like any hitter, he spends some swings working on techniques -- advancing a runner with groundballs to the right side, smacking line drives to the opposite field -- and, yes, even the mandatory bunts down each baseline, to the dismay of fans.
Oh, yeah, and then there's the issue of his bat. During one day of batting practice last week, for instance, he sprayed liners around the field and struck a few more baseballs that didn't seem as lively in their trajectories as one might expect.
That's because he was swinging a veritable tree trunk, a practice-only bat of 36 inches and 36 ounces. For his final round of swings, however, he switched to his lighter, game-use Marucci bat and dutifully complied with a handful of bombs.
"I try to train with bigger bats, so when I go into the game, it just feels a lot better," said Harper, who in batting cages has even swung a whopping 47-ounce bat.
His early spring returns suggest he's kept a disciplined approach at the plate through his first four Grapefruit League games, in which he's gone 5-for-11 (.455; all singles) with a walk and two strikeouts.
Such restraint not to swing for the fences is impressive, given that he's possibly baseball's hottest topic of conversation. The 6'3", 225-pound, lefty-swinging, rightfield-playing Harper is the subject of frequent lunch-room talk at tables populated by scouts or media -- and not just in Nationals camp.
Washington general manager Mike Rizzo has fielded question after question about his young prodigy and done so in stride.
"I like talking about him," he said with a smile.
He should. Harper has not disappointed since being drafted No. 1 overall in 2010 and receiving $9.9 million in signing bonus and first four years of salary. He crushed Class A pitching -- .318/.423/.554 with 14 home runs in 72 games -- though his performance in Double A (.256/.329/.395 with three homers in 37 games) was down a few ticks. Perhaps understandably: He skipped High A ball altogether, was the younger player at his level, started slowly and later injured his hamstring.
Upon recovering, Harper played in the Arizona Fall League and batted .333/.400/.634 with six home runs in 25 games while sharing an outfield with the game's other 19-year-old super-prospect, the Angels' Mike Trout.
Nationals manager Davey Johnson -- who held the same position with the Mets when 19-year-old Dwight Gooden made team out of spring training in 1984 and went on to win NL Rookie of the Year and finish second for the Cy Young -- has encouraged Rizzo to give proper consideration to Harper this spring.
Rizzo seems more inclined to bring Harper along slowly given that the player hasn't even had 600 professional plate appearances yet -- but Rizzo is certainly willing to listen and evaluate.
"I think we'll see him in 2012," he said shortly before Grapefruit League play began. "We're not sure when. We're going to be open-minded about early in the season, him breaking camp with us. If it's right for him and the right fit [for us], we'll be open-minded about it. We just have to make sure that he's fully ready to play in the big leagues. I don't want to bring him to the big leagues, have him struggle and fail and have to bring him back to the minor leagues. He's going to be a terrific major league player.
"I've been in player development for a long time and I think I have experience on when guys are ready to go, what it takes to get ready, and I'm going to have an open mind but he has to prove that he's ready -- mentally, physically and emotionally ready to withstand the rigors of the big league season."
The rest of the NL East certainly wouldn't mind seeing Harper stay in the minors a little longer.
"I don't think Harper's ready," Braves manager Fredi Gonzalez, suppressing a laugh, joked earlier this spring. "I think they should leave him down there."
Harper has never been shy, on or off the field, and his occasional brashness has turned some people off. Most recently, he said he wanted to be a "cultural icon" like Joe Namath. Soon thereafter, an unidentified conspirator replaced the HARPER 34 nameplate above his locker with NAMATH 12.
But since being in camp, he's been trying to fit in. Soon after Johnson expressed wariness of social media, Harper deleted his Twitter account. And when the club held a press conference to announce third baseman Ryan Zimmerman's contract extension, not only was Harper one of the first players to arrive, but he also remained standing despite eight chairs being unclaimed. He knew veterans were coming, and he is, after all, only a rookie.
"Everyone makes mistakes," Zimmerman said. "I'm going to make mistakes. He's going to make mistakes. The hardest part is learning from them and getting over them quickly. Obviously he hasn't had too much failure in his life. I think the best thing to happen to him last year in the minor leagues was to struggle a little bit and have to rebound and bounce back, which he did."
Harper is no shrinking violet when it comes to challenges. He has said he hoped to make the majors last year as an 18-year-old, and he sounded disappointed when he didn't face teammate Stephen Strasburg -- one of the game's best young pitchers and the only recent prospect who can relate to Harper's hype -- in live BP.
It also robbed spectators of settling, once and for all, who'd win the baseball prospect edition of the immovable object vs. the irresistible force.
"Absolutely, I wanted to face Stras so bad," Harper said. "I wanted to see what he was about. If he made me look stupid, I didn't even care. It'd just be fun and step in there and see what he looks like from that angle."
His first extravagant purchase with his bonus money was to buy a dream house for his mother near where he grew up in Las Vegas.
"That's a dream come true," Harper said. "I've been telling her I would since I was eight, nine years old."
And when will he start investigating the housing market in the D.C. area for himself?
"Hopefully this year," he said, a smile on his face growing. "Hopefully in about seven weeks."