The long ball came Sunday in the Nationals' 6-5 win against the Reds at Great American Ball Park in Cincinnati. Washington led 5-3 in the top of the ninth inning when Harper stepped up to the plate with one out away in the frame.
Harper had two swinging strikes, a foul ball and two balls before getting a sixth offering from Reds right-hander Raisel Iglesias.
Just before the next pitch, a fan yelled "overrated." The Reds reliever tossed in a 95.5 mph slider. Harper hacked at the pitch, smacking it for a 425-foot home run to center field.
But the dramatic bomb wasn't even Harper's only home run on the day. He also touched 'em all in the sixth inning, hitting a solo shot to right field off of Reds righty Sal Romano.
The 2015 National League MVP and five-time All-Star finished the day 2-for-4 at the plate with two RBI and a walk. He also scored two runs.
"We talk about it all the time, we want to put the pressure on the other team from the get-go," Nationals manager Dave Martinez told reporters after the game, according to MLB.com. "We've been doing that, and it's good to see. These guys are playing with a lot of energy right now. I know it's only the first three games, but I like what I see."
Harper now has 152 career home runs and two on the season.