AP Sports Writer

MIAMI (AP) — The Miami Marlins gave up a franchise record four home runs in one inning, and manager Don Mattingly still found reason to be encouraged about his pitching.

Adam Conley shut out the Washington Nationals for six innings before tiring in a 7-0 loss Tuesday.

Bryce Harper hit a grand slam off Chris Narveson, one of four home runs in a seven-run seventh.

"If you didn’t watch the game, you think it’s a horrible game," Mattingly said. "It was really a well-pitched game, other than some pitches in the seventh."

Conley (0-1) allowed only four hits in the first six innings, extending his scoreless streak to 12 innings in a duel with Stephen Strasburg (3-0).

"That young man was throwing well, big time," Nationals manager Dusty Baker said. "The next thing you know, we had seven runs."

Conley gave up four runs in 6 2/3 innings.

"It’s really encouraging watching him pitch," Mattingly said. "This guy pitches like your ace. He’s attacking on the inside. He came after these guys like he had no fear."

But in the seventh, the Nationals had an answer. Jayson Werth hit his 200th career homer with one out to make it 1-0, and Wilson Ramos homered on the next pitch.

"Strasburg and I had been trading punches the whole game, and those hitters were waiting for an opportunity," Conley said. "My process was really good until I took a breath there in the seventh. That kind of shows my immaturity."

After Washington loaded the bases, Harper hit his seventh homer. Ryan Zimmerman followed with a solo homer, his first.

"Everybody got together and started rolling," Harper said.

Harper has homered in five of the past six games, and has 20 RBIs.

"What he’s doing is pretty special," Werth said. "He has really coming into his own. He’s one of the best players in the game, and he’s got good guys around him too. That helps."

The grand slam was the second of Harper’s career, and his second in five days. Strasburg happened to be on third base for both.

"It was weird being on third again for another Harper grand slam," Strasburg said. "I guess it’s all on me — I’ve just got to get to third."

The dimensions at Marlins Park were shortened before the season, but only Zimmerman’s home run benefited from the cozier confines. Ramos’ homer bounced off the top of the fence.

Washington’s Daniel Murphy, who came into the game leading the majors in batting, went 2 for 4 to hike his average to .422. Strasburg had two singles to raise his career average to .149.

"Everybody is swinging the bat well," Harper said. "Even Strasburg."

The right-hander also lowered his ERA to 1.25. Strasburg struck out 10 while pitching three-hit ball for eight innings.

He gave up an extra-base hit for the first time this year when Giancarlo Stanton doubled with one out in the fourth, but he advanced no farther.

The Marlins fell to 1-6 at home.

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