If you were one to have those doubts, you must not have seen much of Harper over the last two seasons.
In his first big league at-bat in 36 days, Harper took the first pitch he saw from Brewers starter Yovani Gallardo for a ball and then smoked a 93 mph fastball over the left field wall and into the visitors' bullpen for a solo home run.
Harper sprinted around the bases, the Nats Park crowd erupted and the Nats took a 1-0 lead on Harper's 13th homer of the season.
Well after Harper entered the Nats' dugout to high fives and fist pounds from his teammates, the fans here were still standing and cheering. Harper eventually came out for a curtain call, his first since opening day, when he hit two home runs in his first two at-bats of the season.
Harper wowed fans last season during his National League Rookie of the Year campaign. He made headlines on opening day with his two bombs. And despite having missed over a month due to left-knee bursitis and getting just four rehab games before returning to the Nationals' lineup, he still found a way to deliver some magic.
We should just start expecting it at this point.
Update: The offensive roll the Nats have been on the last 30 hours is bordering on ridiculous.
Three innings into tonight's ballgame, the Nats have a 6-0 lead and have pounded out five extra-base hits. After Harper's homer in the first, Jordan Zimmermann, Jayson Werth, Adam LaRoche and Ian Desmond all delivered doubles in the third, and with the five-run frame, the Nats have a comfortable edge a third of the way through this one.
They've now put up 15 extra-base hits and 19 runs in their last 12 innings dating back to yesterday's 13-2 win over the Mets.
On a smaller scale, over their last five innings, the Nats have scored 14 runs.
Two of those came off Mets catcher Anthony Recker, who pitched the ninth inning yesterday, but still, this is just nuts.
Zimmermann usually doesn't need a heck of a lot of run support, but he's getting plenty today.
Update II: Make it 8-2.
The Nats strung together three straight hits to open the fourth (one of which came from Zimmermann, who is now 2-for-2), and Werth's second two-run knock of the game briefly gave the Nats an eight-run edge.
Zimmermann then allowed two runs in the fifth, spoiling the shutout chance, but he's still thrown just 59 pitches through five innings. The bullpen might not be needed for much tonight.
Update III: Zimmermann cruised through his first three innings of work and made it seem like he'd be working deep into yet another ballgame. He ended up going just six, and the Brewers have suddenly made this a ballgame again.
What once was an eight-run Nats lead has been trimmed to three as the Brewers put up four runs on Zimmermann and then got to Craig Stammen for a run in the seventh.
It's 8-5, and remarkably, Rafael Soriano might actually be needed tonight.
Zimmermann has been tremendous this season in tight ballgames and on nights where the Nats give him minimal run support. When he does happen to be handed a big lead, however, his performance suffers. He blew a four-run lead against the Orioles and got stuck with the loss and then lost a five-run lead in a no-decision against the Indians.
Weird stuff. The Nats still hold the lead, but things have gotten a bit more tense in the late innings than we thought they'd be.