Star pitcher Stephen Strasburg gave up a career-high seven runs in five innings as the Nationals lost their fifth game in a row.
After winning his previous four starts, Strasburg allowed five runs, gave up nine hits and struck out only three. He leads the NL with 186 strikeouts.
Miami's Ricky Nolasco claimed his third career shutout and eighth complete game.
There was also a 9-0 scoreline in Pittsburgh where Pedro Alvarez homered twice as the Pirates thrashed the St Louis Cardinals.
Pittsburgh moved within two games of the Cardinals in the race for the NL's second wild-card spot after the visitors played most of the game without catcher Yadier Molina, who suffered neck, back and shoulder injuries following a violent collision at the home plate with Pittsburgh second baseman Josh Harrison.
In total there were six shutouts in Tuesday's 15 games, with Tommy Milone and three Oakland relievers extending Cleveland's scoreless streak to 22 innings as the Athletics beat the Indians 7-0.
It was the A's fourth win in a row and they remain tied with Baltimore at the head of the AL wild-card race, with the Orioles another team not to concede a run.
Chris Tillman allowed just one hit over seven innings and Nick Markakis drove in three runs as the Orioles beat the Chicago White Sox 6-0.
The other shutouts saw the Texas Rangers beat the Tampa Bay Rays 1-0 and the Atlanta Braves win 2-0 at the San Diego Padres, but there were runs elsewhere.
The Cincinnati Reds beat the Arizona Diamondbacks 5-2 to make it three wins in four games and stretch their lead in the NL Central to seven games over the St Louis Cardinals.
Jeff Bianchi hit a three-run shot for his first home run in the major leagues to lead the Milwaukee Brewers to a 4-1 win over the Chicago Cubs, while the Colorado Rockies beat the Los Angeles Dodgers 8-4.
Pinch-hitter Hector Sanchez hit the go-ahead RBI single in the ninth inning as the San Francisco Giants came from behind to beat the Houston Astros 3-2, while Mike Moustakas had three hits and three RBIs as the Kansas City Royals beat the Detroit Tigers 9-8.
Justin Verlander, the reigning AL MVP and Cy Young Award winner, was charged with eight earned runs, matching his career high, in five and two-third innings.
Hisashi Iwakuma was much harder to hit as the Seattle Mariners beat the Minnesota Twins 5-2, while the New York Yankees handed Ricky Romero his 11th straight loss with a 2-1 victory over the Toronto Blue Jays.
Ike Davis hit a tie-breaking double during a four-run 10th inning as the New York Mets beat the Philadelphia Phillies 9-5, while the Los Angeles Angels scored twice in the ninth inning to beat the Boston Red Sox 6-5.