Jose Fernandez and three Miami relievers held Washington to six hits in a 6-1 Marlins win on Monday.
Fernandez (1-1, 3.78 ERA) gave up a run on three hits in six innings, striking out nine and walking four.
The Marlins (4-7) jumped out to a 3-0 first-inning lead on a Christian Yelich RBI single and a two-run single by Marcell Ozuna.
Giancarlo Stanton homered for Miami, his third of the season, in the fifth.
The Nationals (9-3) got their only run on a fifth-inning sacrifice fly by Bryce Harper.
Tanner Roark (1-2, 3.71 ERA) took the loss, giving up five runs, four earned, on seven hits in six innings of work.