Bryce Harper continued his magnificent May with another homer.
The New York Yankees, meanwhile, will have to make do without their leading hitter for the foreseeable future.
The visiting Yankees will be without Jacoby Ellsbury on Wednesday night when they seek a two-game split against Harper and the red-hot Nationals.
Harper is hitting .535 in a 10-2 stretch for Washington, with all of his 10 homers and 23 RBIs this month coming in that span. He homered in his first at-bat in Tuesday's 8-6, 10-inning victory before drawing a walk, hitting into a double play and striking out twice over the remainder of his night.
"The way he's swinging the bat, any way you get him out, we'll take it," Yankees manager Joe Girardi said. "Our guys did a really good job."
Harper leads the majors this month in homers, RBIs and OPS (1.503). He is 9 for 15 with three homers and seven RBIs in the Nationals' four-game win streak.
While there is no doubt Harper will be penciled in Washington's lineup, New York (22-18) won't be able to insert Ellsbury. The center fielder is heading to the 15-day disabled list with a sprained right knee suffered Tuesday.
Ellsbury, batting a team-high .324, was replaced by Carlos Beltran. The Yankees, losers of six of seven, said that outfielder Slade Heathcott would be called up from Triple-A Scranton-Wilkes-Barre on Wednesday.
"It's not what you want but if we are going to lose him for some time, somebody's gotta step up," Girardi said.
Washington (23-17) got a winning two-run homer from Ryan Zimmerman to complete a rally from a four-run deficit.
"The fact that we got back into it is a credit to the offense," manager Matt Williams said. "Getting back into that game, it's easy to pack tents and say it's not our night, but we don't do that."
Zimmerman's blast accounted for the first runs allowed by Yankees closer Andrew Miller.
''He's not going to be perfect,'' Girardi said about Miller. ''You know, he gave up his first run."
Nationals starter Jordan Zimmermann (3-2, 3.66 ERA) is 5-0 with a 1.87 ERA in eight career home interleague outings. That includes a 5-3, 14-inning loss to New York in which he gave up three runs over six innings on June 16, 2012.
The right-hander struck out six in six innings Friday to earn a 10-0 win at San Diego in Washington's fourth straight victory with him on the mound.
Zimmermann has faced Chase Headley the most among Yankees hitters, with the third baseman going 3 for 19. He has never faced Alex Rodriguez, who was not in Tuesday's lineup with New York playing in an NL ballpark.
Washington catcher Wilson Ramos homered Tuesday to extend his career-high hitting streak to 19 games. He is batting .365 with 12 RBIs during his run.
The Yankees' Adam Warren (2-2, 4.50) will make his first career interleague start and first appearance against Washington. The right-hander yielded three runs in a career-high seven innings in last Wednesday's 3-2 defeat at Tampa Bay.
Yunel Escobar, who is 2 for 5 off Warren, is 7 for 16 with six runs scored in his last four games.