The decisive eighth inning started with pinch-hitter Scott Hairston, who doubled off left-hander Brad Hand. Then, taking orders from the dugout, Denard Span reached base on a bunt base hit. The play was a close one at first, drawing a challenge from Marlins manager Mike Redmond, but the ruling was that the call stands.
"I thought he was still out," Redmond said after the game. "The views I had, I thought he was out. Definitely, at that point in the game, it was a play worth replaying. That play was huge. It looked like [second baseman Jordany Valdespin] caught the ball before he touched the base."
After Span stole second to put runners on second and third, Jayson Werth hit a go-ahead sacrifice fly to left field off Marlins reliever A.J. Ramos, scoring Nate McLouth, who was pinch-running for Hairston.
After Adam LaRoche drew a walk and stole second base, Ian Desmond doubled to left field, scoring Span and LaRoche to make it a three-run game.
LaRoche stealing second and scoring proved to be the difference in the game.
"We had a good feeling [the Marlins] were not going to throw [to second], so Adam timed the pitcher and went to second. It turned out to be the difference run for us," manager Matt Williams said.
Two of the three runs in the eighth were charged to Hand, who pitched seven-plus innings and allowed three runs on five hits.
The run support helped Roark win his team-leading 11th game of the season. He allowed one run on three hits and struck out seven in his seven innings. It marked the sixth straight game in which a Washington starter pitched at least seven innings and allowed two runs or fewer.
After starting the game by walking Christian Yelich, Roark retired the next nine hitters he faced. Roark's only blemish occurred in the fourth inning, when Valdespin hit a monster home run that landed in the right-field upper deck.
"Tanner continues to pitch well for us," Williams said. "He gave up the home run to Valdespin. Other than that, he pitched pretty well, he kept us in the game, allowed us to get some opportunities."
After Roark left the game, Tyler Clippard threw a scoreless eighth, but the Marlins made it a game in the ninth inning off reliever Drew Storen, who picked up his first save since Aug. 22, 2013, against the Cubs.
Closer Rafael Soriano was not available for the second day in a row because he was overworked. So in came Storen. It started with Giancarlo Stanton, who hit a monster home run over the right-field wall, his 22nd homer off Nationals pitching during his career.
Storen was able to get two quick outs before Marcell Ozuna singled. Adeiny Hechavarria then doubled down the first-base line, scoring Ozuna to make it a one-run game. Jarrod Saltalamacchia walked and represented the go-ahead run. But Reed Johnson grounded into a force play to end the game.
"Ugly, but I got it done," Storen said. "That's really the main thing. It's about winning the game."
Williams said he wasn't nervous when the Marlins began to rally. He pointed out that Miami has made it a habit of coming back. On Monday, Washington fell, 7-6, after leading 6-0 going into the seventh inning.
"But Drew made a pitch when he had to make a pitch. That's all that matters with us," Williams said.
Williams came away impressed with what he saw from the Marlins during the three-game series.
"The Marlins are a no-quit, talented team," Williams said. "They pitched well, they played good defense. They got speed, they got power. They do a lot of things right. They played us very well."
The Nationals now return to Washington to open an eight-game homestand on Thursday night.