WASHINGTON -- Washington right fielder Bryce Harper came to the plate in the bottom of the seventh inning with a chance to hit his fourth homer of the game Wednesday afternoon.

But there was also something else on his mind, with shortstop Ian Desmond on third base and one out.

"You are trying to get that run in," said Harper, who did exactly that as his ground ball brought in Desmond to give the Nationals a 7-2 lead.

It was the fifth RBI of the day for Harper, who hit homers in his first three at-bats as the Nationals beat the Miami Marlins 7-5.

Harper, 22, became the 10th-youngest player in major-league history to hit at least three homers in a game. It was the first three-homer game of his career in the majors; Harper said he hit four in a game twice in his only season of junior college.

"One of the better moments of my career," said Harper, who hit three homers for Double-A Harrisburg during a rehab assignment last season. "I'm trying to be a little more aggressive."

"Pretty impressive -- three homers," said Washington reliever Tanner Roark, who pitched a scoreless eighth inning after Harper drove in his fifth run.

Harper, who has eight homers this year, had his red Nationals hat on backward during a postgame interview as he wore a gray T-shirt with the letters "GOOD LUCK" on the front -- except the K was written backward to note a called third strike in baseball parlance.

Marlins starting pitcher Tom Koehler certainly didn't have much luck -- let alone get a called third strike -- against the locked-in Harper. The right-hander allowed all three homers by Harper, who entered the game with just two hits (including a homer) in 15 career trips to the plate against the former Stony Brook standout.

"Just one of those days. He made a couple of mistakes up in the zone," Marlins manager Mike Redmond said of Koehler.

The winning pitcher was Max Scherzer (2-3), who gave up 10 hits and five runs in seven innings. He was allowed to face right fielder Giancarlo Stanton in the seventh, and the slugger hit a three-run homer to pull the Marlins to within 7-5.

"I have ultimate confidence in Max Scherzer no matter who is standing at the plate," Washington manager Matt Williams said.

Harper became the fourth Nationals player to hit three homers in a game, joining Alfonso Soriano, Adam Dunn and current first baseman Ryan Zimmerman.

On Harper's third homer, a solo shot in the fifth, Stanton didn't even move as the blast landed in the second deck and gave the Nationals a 5-2 lead against Koehler (2-3).

Moments later, Harper took a curtain call out of the dugout as he raised his right arm to an appreciative crowd. "I didn't want to go up there," Harper said, adding he wanted to hit another homer.

Washington third baseman Yunel Escobar had an RBI single in the seventh to pad the lead to 6-2 against reliever Sam Dyson and Harper drove in a run on the groundout to make it 7-2. The Nationals had scored three in the third to take a 4-2 lead on an RBI single by Desmond and a two-run homer by Harper, who now has 20 RBIs. Harper cut the lead to 2-1 with a solo shot to lead off the second.

Miami had taken a 2-0 lead in the top of the second with back-to-back RBI singles by left fielder Ichiro Suzuki and shortstop Adeiny Hechavarria.

Scherzer allowed five earned runs and 10 hits in seven innings while Koehler yielded five earned runs and seven hits in six innings.

The Nationals (14-15) have won seven of their last nine games, and the Marlins (13-15) lost for the third time in four outings.

Marlins second baseman Dee Gordon and third baseman Martin Prado each had three hits. Washington center fielder Denard Span, catcher Wilson Ramos and Desmond had two hits, as did Miami first baseman Justin Bour and catcher J.T. Realmuto.

Even with the heroics of Harper, the Marlins had the go-ahead run at the plate in the ninth.

"We had a shot," Redmond said. "We had that chance. We had an opportunity there at the end."

NOTES: The Nationals will open a three-game series with the Atlanta Braves at home Friday and will send LHP Gio Gonzalez (2-2, 3.86 ERA) to the mound to face Atlanta LHP Eric Stults (1-2, 4.91). ... The Marlins start a West Coast trip Thursday against the San Francisco Giants as RHP Dan Haren (3-1, 2.70) faces Giants RHP Tim Hudson (1-2, 3.78). ... Washington RHP Stephen Strasburg left Tuesday's start after three innings as he complained of an irritation under his right (pitching) shoulder blade. Manager Matt Williams, on his weekly radio appearance, said Wednesday that he does not expect Strasburg to land on the disabled list. "We'll see how he progresses through the next two or three (days) and see where he's at," Williams said. "But, at this point, I wouldn't envision a DL stint. But, again, it depends on how he feels and what he can and can't do." Strasburg threw on flat ground after the game Wednesday. ... Marlins 1B Justin Bour, who made his big-league debut last year against the Nationals, was in the starting lineup for the third game in a row. He is hitting .500 in 18 at-bats. 1B Michael Morse, who did not play in the series, is hitting .193 in 88 at-bats.