Stephen Strasburg won his second straight start since returning from the DL in a 3-2 Nats win over Philadelphia in the opening game of a doubleheader on Sunday.
Strasburg (5-5) gave up two runs on four hits in seven innings of work, striking out nine and walking one.
The Nationals won despite hitting just 2-for-12 with runners on scoring position and leaving 13 men on base, including seven in the last four innings.
Drew Storen pitched a perfect ninth for his 23rd save.
Washington (42-33) has now won eight games in a row, and has a three and a half game lead over the New York Mets in the National League East.