MIAMI -- Emergencies are Yusmeiro Petit's specialty.

When starting pitcher Joe Ross developed a blister on his right middle finger early in Wednesday night's game, the Washington Nationals sounded their alarm.

Petit heard it and responded to help the Nationals defeat the Miami Marlins 3-1 at Marlins Park.

The Nationals also got RBI doubles from Bryce Harper and Ryan Zimmerman and a solo homer by Michael Taylor, but Petit and the bullpen earned the headlines.

Four Washington relievers combined to pitch seven innings, allowing just one run. Petit (1-0) led the way with four innings worked.

"Petit's job -- the long man out of the bullpen -- is the hardest job in baseball," said Nationals closer Jonathan Papelbon, who worked a scoreless ninth to earn his sixth save of the season. "He's a consummate pro. He handles his role well."

Papelbon did his job, too, striking out Giancarlo Stanton to end the game. Stanton, who has averaged 32 homers per season the past five years, represented the tying run, but he was caught looking at a Papelbon fastball for strike three.

"I was hoping it didn't get to that, but it always does," Nationals manager Dusty Baker said of having to face Stanton with the game on the line. "It was similar to the days when we wanted Albert Pujols to be on deck when the game ends because you are counting and saying, 'We don't want this guy to get up there. He can tie this game up with one swing.'

"But (Papelbon) was dealing."

Harper, who leads the majors in RBIs, drove in his 21st run to lead a modest effort by Washington's offense.

Nationals second baseman Daniel Murphy went 2-for-4 to extend his hitting streak to 12 games, the longest active run in the National League. Murphy leads the majors with a .429 batting average.

Meanwhile, Nationals left fielder Jayson Werth left the game due to tightness in his hamstrings. Baker, who had already planned to give Werth Thursday off, does not think it's a serious injury.

The other injured Nationals player, Ross, lasted just two innings, allowing one hit, one walk and no runs.

"Joe had a serious blister," Baker said. "We tried to send him back out there, but it looked too ugly."

Baker said he is not sure if Ross will have to miss a start.

While Ross went short, Marlins starter Wei-Yin Chen pitched seven innings, allowing six hits, two walks and three runs, striking out seven.

Chen's performance was solid but not enough.

"I got ahead in the count, but I couldn't finish some hitters," Chen said. "I have to do a better job."

Washington got to Chen quickly. In the first inning, Anthony Rendon drew a four-pitch walk and scored on a two-out double to left-center by Zimmerman.

The Nationals made it 2-0 in the third. Ross walked on a 3-2 pitch and scored when Harper lined a 0-2 delivery for a double over the glove of center fielder Ichiro Suzuki. Harper has at least one RBI in seven straight games.

After that, Petit took over on the mound for Washington.

"I like emergencies," Petit said. "I knew I had to cover those innings until the sixth or seventh, and I like helping the team."

Taylor gave Washington a 3-0 lead when his solo home run in the fifth inning barely made it over the wall in right-center. It was his second homer of the season.

Miami got that run back in the bottom of the fifth on a solo home run by Derek Dietrich, who pulled a 1-2 pitch from Petit over the wall in right.

But that was all Miami's offense could manage.

"Anytime you don't hit, you feel a little flat," Marlins manager Don Mattingly said. "When that's going on, it's always a battle. (The Nationals) were keeping us off stride, changing speeds, and we weren't able to break through."

NOTES: The Marlins are 4-4 this season against the top two teams in their division, the Nationals and Mets. ... Nationals manager Dusty Baker asked for -- and received -- a signed bat from Marlins CF Ichiro Suzuki and 2B Dee Gordon. Baker said he is giving the bat to his son. ... Nationals OF Ben Revere, who went on the disabled list on April 6 due to a right oblique strain, is working out with the team but is not yet close to a return. ... Marlins manager Don Mattingly turned 55 on Wednesday. ... Mattingly said Nationals RHP Joe Ross is particularly tough on right-handed hitters. For that reason, Mattingly stacked his lineup -- five of his first six batters are left-handed hitters, including non-regulars Suzuki and 3B Derek Dietrich. ... Mattingly rested CF Marcell Ozuna and 3B Martin Prado. ... Marlins LHP Mike Dunn, who has been out since March 25 with a strained right oblique, is not yet able to throw.