You could see his power in the form of the two homers he crushed to right field. He showed off his arm in the eighth, when he held both runners on a fly ball to center. And there was his "100 percenter" attitude, as manager Davey Johnson put it, which led to his first Major League ejection in the ninth inning after he slammed down his helmet when he couldn't beat out a double-play grounder.
"I felt good up there. I think that's what [ticked] me off the most," Harper said, referring to his big day at the plate and his ejection. "When you feel good up there and you roll [stuff] over and you miss some pitches you should drive, I think that makes you more upset. I think going up there, I felt really good today. I saw some pitches that I could drive and did some damage."
For all the attention the 19-year-old's second-half slump has received, he is hitting .293 (12-for-41) with two doubles, a triple and four homers over his last 11 games, 10 of them starts. He helped his cause, and that of the slumping Nationals lineup, by blasting a two-run shot 355 feet to right field in the fourth inning.
That gave Washington its first lead in more than a week and came amid a four-run frame against Marlins rookie Jacob Turner, who sat down the Nationals in order the first three innings.
"This ballclub, they can hit. This ballclub is in first place for a reason," Marlins manager Ozzie Guillen said. "When you face those guys the second time in the lineup, you've got to be more careful."
Michael Morse hit a ball even farther than Harper's, albeit to the wrong part of the spacious Marlins Park outfield, and drove in Adam LaRoche with a triple to center -- his first triple since Aug. 27, 2010. Ian Desmond then drove in Morse with a single to right field.
But Harper wasn't done. With one out in the fifth, he swung at a 3-0 fastball from Turner and launched it an estimated 425 feet -- and almost certainly more than that -- well into the second deck in right field to put Washington ahead, 5-0.
"He's learning about himself and how he reacts to big league pitching," Johnson said. "He's totally committed to 100 percent effort, and sometimes you get a little too aggressive at the plate. And he was much better tonight. The last few days he's been a lot better. I mean, he crushed that second one. ... A lot of good things happened with him."
But the Marlins crawled back. Lefty Ross Detwiler gave up one run in the fifth and two more in the sixth, exiting after 5 2/3 innings. Reliever Ryan Mattheus gave up one run on Greg Dobbs' sacrifice fly in the seventh, but Morse drove in Ryan Zimmerman on an eighth-inning single to give the Nats a valuable insurance run.
Miami threatened once again in the eighth, with Donovan Solano and Jose Reyes hitting their way into scoring position against reliever Sean Burnett. In came Storen, inheriting a two-run lead and a jam with two runners on, no outs and the heart of Miami's order due up.
Storen got Carlos Lee to fly out to center, and Harper's throw eliminated any thoughts of Solano tagging up to score. The reliever nearly hit Giancarlo Stanton in the head with a pitch and then saw the slugger shoot a line drive just foul down the left-field line before finally striking him out. Finally, Storen induced a weak grounder to third from Justin Ruggiano, and Zimmerman's throw to LaRoche ended the threat and a high-wire act.
"Storen won the game for us," Johnson said. "He had to go through a very hot middle of their order, and he made great pitches and got us out of that jam. That won the game."
"Guys were hitting the ball well, so it's our job to lock down that win right there," added Storen. "That was kind of the biggest thing. The hitters had a great day, so you've got to make sure to take care of them and lock down that win."
Finally, about 5 1/2 hours after Johnson called a pregame meeting to talk over their longest losing streak of the season, the Nationals could fly back home with a much-needed win, a commanding lead in their division and the second-best winning percentage in the Majors.
"The makeup on this club is off the chart, and they really don't need a lot of meetings," Johnson said. "They just need to let me let them go play like tonight. It was a fun game."