Fister started and pitched two innings, allowing a run on two hits with two strikeouts. The run scored in the second inning, with Derek Dietrich scoring on a single by Reed Johnson.
The score was tied at 3-3 when Washington went ahead to stay in the fifth inning against right-hander Bryan Evans. Nate McLouth led off with a single and scored on a triple by Jeff Kobnerus. Ian Desmond followed with a groundout, but Kobernus scored on the play to make it 5-3.
The Nationals added to their lead by scoring four more runs in the bottom of the seventh. Matt Skole highlighted the scoring with a two-run double. The runs were charged to left-hander Edgar Olmos.
The Marlins had a 2-1 lead after three innings, when right-hander Chris Young allowed a solo home run to Ed Lucas.
Marlins left-hander Brian Flynn was on the mound when first baseman Adam LaRoche hit a two-run homer to give the Nationals a 3-2 lead.
But Miami would tie the score at 3-3 in the fifth inning off reliever Craig Stammen. Greg Dobbs scored on a double by Donovan Solano.
Up next: The Marlins will return home to Roger Dean Stadium on Monday to host the Astros at 1:05 p.m. ET. Right-hander Jacob Turner will see his first game action of the Grapefruit League schedule. The 22-year-old, who is likely to make Miami's starting rotation, is coming off a season in which he went 3-8 with a 3.74 ERA in 20 starts.