WASHINGTON -- Joe Ross was supposed to pitch on Saturday, but the game was called due to inclement weather.

The young right-hander certainly pitched on Sunday, and his first start of the season was impressive.

He gave up a leadoff triple to Dee Gordon, who eventually scored, but Ross, 22, allowed just that one run on five hits in seven innings as the Washington Nationals beat the Miami Marlins 4-2 to split the two-game series.

"He knows what he is doing. He is not intimidated," said Dusty Baker, the Nationals first-year manager. "He had quite a few 3-2 counts. He made some pitches when he had to. (Ross is) beyond his years in maturity."

Ross (1-0), who made his big league debut last June, also had a solid single in the second inning but was stranded. Teammates were kidding him in the clubhouse about his hit as he tried to talk to reporters about his day on the mound.

The California native said his improved changeup was effective against the Marlins, while his slider was passable.

"I think I just got into my rhythm" after the Gordon triple, Ross said. "The changeup was good. I got some big outs with it."

"We were not able to do a lot with him," Marlins manager Don Mattingly said of Ross, who was making his first career start against Miami.

Said Washington outfielder Bryce Harper of Ross: "What more could you say about Joe Ross today? He had everything going."

Ross was credited with the win as Jayson Werth broke a 1-1 tie in the seventh with a bases-loaded single with one out. It was the first hit of the season in 14 at-bats for Werth, whose hit came against former teammate Edwin Jackson.

"That was a big at-bat for (Werth) right there," Harper said.

The blooper into short center scored Anthony Rendon, who singled for his third hit of the game, and went to third on a double to left-center by Harper -- the 100th of his career -- against lefty Chris Narveson.

"Chris is capable of getting him out," Mattingly said of the hit by Harper.

Daniel Murphy was given an intentional walk to load the bases before Jackson came on to face Werth.

"He got two quick strikes on him and wasn't able to put him away," Mattingly said of Jackson going against Werth.

Two batters later Clint Robinson drove in two runs with a sharp liner to left-center off Jackson to make it 4-1.

"He wasn't able to polish him off either," Mattingly said of Jackson.

Blake Treinen pitched a perfect eighth for the Nationals and Jonathan Papelbon tossed the ninth for his third save in as many tries. He gave up a solo homer with one out to Christian Yelich, then retired pinch-hitter Derek Dietrich on a grounder for the final out with a runner on base.

Harper had an RBI double in the first to drive in Rendon, who had singled, to tie the game at 1-1 against Marlins starter Tom Koehler (0-1).

Giancarlo Stanton had an RBI single in the first to drive in Gordon and give the Marlins a 1-0 lead.

The Marlins have dropped eight of their last 11 games at Nationals Park and have not had a winning season in Washington since 2011. The Marlins were 26-9 in their first four seasons at Nationals Park and are 11-29 since then.

Koehler entered the game with a lifetime mark of 3-6 with an ERA of 4.64 against the Nationals.

"I didn't really have a good feeling in the first," Koehler said. "As the game went on I felt like I got stronger. I had a feeling that would probably be my last batter either way (in the seventh against Rendon). I threw the pitch that I wanted and he did a great job hitting it. There was not really anything else I could have done."

Murphy and Harper had two hits for the Nationals, while Murphy (hitting .462) reached in his four at-bats with two singles and two walks. Gordon and Martin Prado had two hits for the Marlins.

NOTES: The Marlins challenged a call in which 2B Daniel Murphy beat out an infield single with two outs in the fifth to load the bases. The Marlins lost the challenge, but LF Jayson Werth grounded out on the next pitch to end the threat. ... Washington 1B Clint Robinson got the start Sunday in place of regular 1B Ryan Zimmerman, as manager Dusty Baker tries to get days off for some of his regulars. Robinson played in 126 games last season in his first full year in the majors and hit 10 homers. ... Washington RHP Max Scherzer, originally slated to start Sunday, will face the Atlanta Braves on Monday at home after Saturday's game was postponed due to cold weather. ... The game-time temperature was 43 degrees.