John Lannan gave up eight runs in five innings and the Phillies failed to put together a winning streak for the first time since the All-Star break in a 9-2 loss to the Nationals.
Anthony Rendon and Ryan Zimmerman both went deep on Lannan, who dropped to 3-5 and saw his ERA rise to 4.81.
Lannan had faced his former team twice before this season -- though both games were at Citizens Bank Park -- and had held the Nats to two runs and 10 hits in 13 innings.
Friday night he struggled with control and walked five, including pitcher Dan Haren with the bases loaded in the fifth. Of his 95 pitches, just 52 went for strikes.
The offense sputtered against Haren, who threw his second straight good outing. Only three Phillies picked up hits: Michael Young, Domonic Brown, and Chase Utley had a pair.
Cesar Jimenez pitched well again, albeit in a low-pressure situation again, retiring Washington in order in the seventh.
The Phillies are 4-15 since the break and are just 8.5 games ahead of the last-place Marlins. The Nationals broke a four-game losing streak.
Cliff Lee (10-5, 3.13) opposes Taylor Jordan (1-3, 3.76) Saturday night.
Another Int'l splash
The Phillies added yet another third base prospect today, signing No. 4 international prospect Luis Encarnacion to a $1 million signing bonus, according to Baseball America.
The 6-foot-2, 195-pound 16-year-old reportedly has raw power and hits from the right side. The Phillies already have Cody Asche in the majors and Maikel Franco waiting in the wings at third base at Double-A.