The loss pushed the Phillies to the brink of elimination. One more Phils loss or one more win by the St. Louis Cardinals will officially end the Philadelphia baseball season.
"We just have to try to finish off positive," said first baseman Ryan Howard.
An optimist might point out that the Phillies' 40-41 home record isn't that bad considering they were once 17-29.
A pessimist would suggest that more was expected out of the five-time defending National League East champions, regardless of the number of injuries.
Bryce Harper, who won't turn 20 until Oct. 16, hit his 21st home run in the first inning to get the Nationals on the board.
The Phillies struck back in the bottom of the first on Darin Ruf's three-run double to center against now-21-game-winner Gio Gonzalez.
"It was 2-0, and he had to come in with a pitch around the zone, and I was aggressive," Ruf said. "It was a fastball, a pretty good pitch down, but I stayed through it and hit it over Bryce's head."
Ruf was one of the bright spots, going 2 for 4 with three RBIs.
In his brief time with the Phillies, he is hitting .385 (5 for 13) with five RBIs.
"He looks like a hitter and thinks he can hit," manager Charlie Manuel said after the game.
At first, this looked like a night the Phillies might get to Gonzalez, but it didn't happen. The Nationals lefthander didn't allow another run after that first inning. He pitched six innings, allowing six hits and three walks while striking out six.
"This is how it has gone for us," Manuel said. "We have had trouble with lefties."
It wasn't a vintage performance from the Nationals' Cy Young Award candidate, but he kept Washington in the game until the bats woke up.
No bat did more damage than Michael Morse's. The 6-foot-5, 245-pound leftfielder swatted two home runs, a solo shot in the second and then a two-run bomb to dead center field in the sixth.
In between, he also had an RBI groundout, and finished 2 for 4 with four RBIs.
His two-run shot in the sixth extended the Nats' lead to 6-3 and caused the exit of Phillies starter Tyler Cloyd.
In five-plus innings, Cloyd allowed six earned runs on six hits. Since July 3, 2011, Cloyd has posted a 20-3 minor-league record, but he has found difficulty in the big leagues. His ERA has risen to 4.91.
Against Washington, Cloyd struggled with his command. He threw 90 pitches, 56 for strikes.
"They are a great team with a great lineup, and they definitely made my mistakes pay," Cloyd said.
Contact Marc Narducci at email@example.com, or follow on Twitter @sjnard.