PHILADELPHIA -- Facing one of the NL's top pitchers brought out Kyle Kendrick's best.
Kendrick (8-6) allowed one run and five hits in seven innings to help Philadelphia take three of four from the defending NL East champions.
"He rose to the occasion," Phillies manager Charlie Manuel said. "Zimmermann was real good. Kendrick was right there with him."
The Phillies are 7-3 since July 2, including series wins over first-place Pittsburgh and Atlanta, to pull within 1 1/2 games of the second-place Nationals and one game of .500.
"It's a big win for us," Kendrick said. "I knew it was going to be close. I just wanted to give us a chance and we got some big hits."
Zimmermann (12-4) gave up two runs and eight hits, striking out six in 6 1/3 innings.
"My stuff was good," Zimmermann said. "On the pitch to Frandsen, I didn't get the slider low enough and he just flicked it out there."
Antonio Bastardo pitched a perfect eighth and Jonathan Papelbon finished for his 20th save in 24 tries. Papelbon blew two saves against the Nationals last month and allowed two runs in a 3-2 win Monday night.
Darin Ruf led off the bottom of the seventh with a double down the left-field line. Pinch-runner John McDonald advanced on a sacrifice and scored on Frandsen's RBI double off center fielder Denard Span's glove.
"As a group, all of us are ready," Frandsen said of Philadelphia's bench. "We know there's one spot you're going to have a chance and fortunately I came through."
Frandsen is hitting .355 (11 for 31) with 10 RBIs as a pinch-hitter this season.
"He's very valuable for us," Manuel said. "He's won a few games for us already."
Kendrick overcame a season-high four errors by the Phillies with two double plays and nine groundouts. Chase Utley had a career-worst three errors.
"I just had to battle and keep the game close," Kendrick said.
Utley got the Phillies an insurance run in the eighth by hitting a double to start the inning, moving to third on a fly ball and sliding in safely just ahead of a throw to the plate on Michael Young's grounder to second.
The lead didn't last long.
All-Star Domonic Brown threw out fellow All-Star Harper trying to score from second on Jayson Werth's two-out single to left in the first. That was Washington's first hit with runners in scoring position in the series after going 0 for 16.
David Bell was the last Phillies player to have three errors in a game on May 17, 2005. ... The Phillies lead with the majors with 37 pinch hits. ... The Phillies, who had a streak of 257 consecutive sellouts from July 7, 2009 to Aug. 6, 2012, drew 40,086 fans to fall short of a sellout on Fireworks Night at Citizens Bank Park. ... Werth was 2 for 4 and is batting .328 (40 for 122) with six doubles, six homers and 21 RBIs since returning from the DL on June 4. ... Washington is 5-35 when scoring less than three runs. ... Jonathan Pettibone (5-3, 3.84) faces John Danks (2-6, 4.31) when the Phillies open an interleague series against the Chicago White Sox on Friday night. ... Stephen Strasburg (5-6, 2.45) pitches for the Nationals vs. Miami's Nathan Eovaldi (1-0, 2.55) Friday night.