WASHINGTON -- At last, the Washington Nationals' lineup is starting to click. In related news, Davey Johnson's squad is closer to first place than it has been in over six weeks.
Stephen Strasburg (5-6) allowed four runs over six innings. He matched his season-high with nine strikeouts as the Nationals won their fourth straight, the last three over San Diego.
The victory moved the Nationals within four games of NL East-leading Atlanta. That is the smallest deficit for the defending division champions since May 20.
"We've played below our potential and now we're coming around," Johnson said. "That's a good feeling."
Feeling good isn't in the Padres' repertoire right now.
"That was a rough one. No doubt about it," San Diego manager Bud Black said.
Anthony Rendon hit home run and drove in three runs for the Nationals, who are four games over .500 for the first time since April 12. San Diego lost the final nine times on its 10-game road trip.
In the series finale, San Diego outhit Washington 12-11, but finished 1 for 12 with runners in scoring position. Of course, scoring seven runs is often enough to claim victory. During other parts of the skid, the offense only scored seven runs over six games.
"You're finding different ways to lose each time," catcher Nick Hundley said. "Some days, we pitched great and didn't hit. Other days, we swung great and didn't pitch. You try to find a nice combination of both and go from there."
Zimmerman's slam off Robbie Erlin (1-2) put Washington ahead 5-1 in the third inning.
In his first at-bat, the Nationals third baseman struck out on full count fastball. In the third inning, Zimmerman batted after Harper reached on an infield single off the glove of first baseman Jesus Guzman to load the bases.
With an approach Johnson described as more aggressive, Zimmerman swung at the first pitch -- another fastball -- he saw from Erlin and launched it over the right-field wall.
"I've kind of been the same way my whole career. I take a lot of first-pitch strikes," Zimmerman said. "That kind of gives me fastballs right down the middle with the bases loaded to hit."
Two batters later, Rendon hit a two-run homer.
Rendon and Strasburg had RBI singles during the Nationals' four-run fifth inning. Harper, chosen a day earlier for the NL All-Star team, hit an RBI single in the first.
"I think everybody has been swinging it well," Harper said. "It's good to puts runs up there on the board for Stras."
That certainly hasn't been the case most of the season. In Strasburg's previous four starts, Washington scored four runs total. The rare scoring surge with Strasburg on the mound helped the starter win for the first time in three starts and earn his second victory since May 26.
Strasburg, who started the six-run third inning with a walk, lost his way in spots. He hit three batters, walked two and in the fourth yielded a two-run homer to Alexi Amarista.
"It was a tough day for Stras out there," Johnson said. "He was battling. I thought he threw good. Sometimes he fights himself ... seems like the last couple of weeks he's been snake bit."
The right-hander allowed seven hits, his most since April 7, and never pitched a 1-2-3 inning. But the San Diego native overpowered the Padres when needed. With Washington leading 7-3 in the fifth and two runners on with two outs, Strasburg struck out Kyle Blanks.
"I think it was a good series for us, obviously getting the sweep and gaining some ground," Strasburg said. "Keep swinging like that, I think we're going in the right direction."
Amarista had three hits and drove in three runs, including an RBI groundout in the seventh against reliever Craig Stammen, who allowed three runs in one inning plus three batters.
Replacing Stammen in the eighth with two runners on and Washington leading 11-7, Drew Storen recorded three straight outs.
Making his fourth big league start, Erlin went four-plus innings, allowing nine runs on six hits and four walks.
Chase Headley had three hits and an RBI for the Padres. ... Washington placed LHP Ross Detwiler (lower back strain) on the 15-day disabled list, retroactive to July 4. The Nationals are expected to activated RHP Dan Haren (shoulder) from the 15-day DL to replace Detwiler in the rotation for Monday's series opener at Philadelphia. ... San Diego placed C Yasmani Grandal (right knee sprain) on the 60-day disabled list and called up C Rene Rivera from Triple-A Tucson. ... San Diego returns home for a three-game series against Colorado. RHP Edinson Volquez (6-6, 5.26) opposes RHP Rockies Tyler Chatwood (4-2, 2.75) on Monday.