John Lannan worked eight innings for the first time in nearly four years, as Philadelphia slipped by Washington, 3-2, in the opener of a four-game set.
Lannan (2-3) haunted his former teammates, allowing four hits and two walks while fanning four.
It was the 28-year-old left-hander's longest outing since his eight-inning stint in an eventual 3-2 loss at St. Louis on Aug. 28, 2009, and his first scoreless outing since holding the Mets off the board on five hits over 5 2/3 innings in a 2-0 victory last Sept. 12 for the Nats.
Jonathan Papelbon did his best to reverse that performance, yielding two runs in the ninth, but held on long enough to post his 19th save.
Jimmy Rollins, Domonic Brown and Darin Ruf were credited with an RBI each for the Phillies, while Ben Revere finished 3-for-5 and scored twice to push his average up to .300.
"Lannan pitched a heck of a game. We got the lead and he held his own," Revere said.
Jayson Werth and Adam LaRoche knocked in late runs for the Nationals, who saw their four-game win streak come to an end.
Activated from the 15-day disabled list prior to the contest, Dan Haren (4-10) allowed seven hits and a pair of runs over five full frames. He struck out seven and walked three but remained winless since May 9.
"(Haren) threw the ball very well. I was pleased with his command, I was pleased with his stuff," said Nationals manager Davey Johnson.
Bryce Harper singled and Ryan Zimmerman doubled to start the ninth, then a deep fly to center from Werth brought in the visitors' first run of the contest and a shallower fly by LaRoche plated Harper to make it 3-2.
Papelbon then served up the game-ending fly to center from pinch-hitter Chad Tracy.
The Phils dented Haren in the first. Revere and Rollins belted singles, then both advanced on a double steal. Brown's dribbler up the first-base line scored Revere and left runners on the corners, and a wild pitch moved Brown to second. Michael Young walked to load the bases, and after Delmon Young fanned, Ruf walked to force in another run.
Fernando Abad took the hill for Washington in the sixth and retired the first two batters. However, Revere doubled down the left-field line and came in when Rollins followed with a base hit.
In two starts against Washington this season, Lannan has allowed two runs and 10 hits, along with eight strikeouts and three walks over 13 innings ...Phillies first baseman Ryan Howard has a torn meniscus in his left knee, and is expected to miss 6-to-8 weeks following surgery ... Prior to the contest, the Nats also acquired outfielder Scott Hairston from the Chicago Cubs in exchange for pitcher Ivan Pineyro and optioned outfielder Tyler Moore to Triple-A Syracuse.