The Nationals managed just five hits, while Ramiro Pena homered in the first and Justin Upton in the fifth to help their side to victory.
Yu Darvish pitched seven scoreless innings to help the AL West leaders Texas Rangers to a 3-1 win over the Kansas City Royals.
The Oakland A's kept the pressure on the Texans after they beat the Chicago White Sox 2-0, with Jarrod Parker allowing just two hits in his six and a third innings pitched.
AL Central leaders Detroit Tigers went down 4-2 against the Baltimore Orioles as Chris Davis hit his 20th home run of the season, while the game between the top two in the AL East, the Boston Red Sox and the New York Yankees, was called off in the sixth because of rain, with the New Englanders 3-0 up and claiming the win.
NL West leaders the Arizona Diamondbacks beat the Chicago Cubs 8-4, as Patrick Corbin recorded his seventh straight win, while Buster Posey went four for four to help the San Francisco Giants to a 4-2 win over NL central pacesetters the St Louis Cardinals.
The Pittsburgh Pirates needed 11 innings to beat NL Central rivals Cincinnati Reds 5-4 thanks to Travis Snider's RBI, while the New York Mets lost their third straight game against the Florida Marlins, going down 11-6, with Ed Lucas going four for four with two RBIs.
Tampa Bay Rays ran riot against the Cleveland Indians 11-3 as Yunel Escobar went three for five with a two-run home run.
The Colorado Rockies beat the Los Angeles Dodgers 7-2, the Houston Astros picked up a rare victory, 5-4 over the Los Angeles Angels, and the Minnesota Twins hit four home runs as they hammered the Seattle Mariners 10-0.
The Milwaukee Brewers went down 7-5 at the Philadelphia Phillies, while the Toronto Blue Jays beat the San Diego Padres 7-4 after 11 innings.