WASHINGTON -- The Washington Nationals know they have plenty of work to do to get back into the NL playoff race.
Adam LaRoche hit a two-run home run in the sixth inning to lift Washington to its fourth consecutive victory with a 4-2 win over the Giants.
Nationals starter Gio Gonzalez threw four shutout innings. San Francisco lefty Madison Bumgarner allowed just one run on an infield ground out in his four innings before the rain hit.
"Four wins in a row, that's pretty good," said Gonzalez, who pitched despite a sore back and said the injury will not affect his next start.
LaRoche sent a 1-0 fastball from Giants reliever Guillermo Moscoso (1-1) off the facing of the second deck above the Nationals bullpen in right field. That came after a leadoff single by Ian Desmond and broke a 1-1 tie.
Tanner Roark (2-0) earned the win with two innings of relief after the delay. Rafael Soriano got his 30th save of the season.
"Good little streak we're on," LaRoche said. "Better late than never. But we're still in a hole pretty good so we've got a lot of work to do."
That's because the winning streak has done little for Washington (58-60) in its pursuit of an NL wild-card berth.
It remains 8½ games out of the final playoff spot with just 44 games remaining after the Cincinnati Reds beat the Chicago Cubs 6-4 in 11 innings on Tuesday.
The Giants are struggling after winning their second World Series in three years last season. They are 7-15 over their past 22 games and at 52-66 in last place in the NL West.
"Same thing we've been talking about," San Francisco manager Bruce Bochy said. "We get our hits. We get them out there. We just can't get them in. Again, it came back to get us."
Even with the winning streak, frustrations have mounted for the Nationals in recent days.
Earlier in the 11-game homestand, outfielder Bryce Harper and manager Davey Johnson argued in the dugout late in an Aug. 7 loss to Atlanta.
In the first inning on Tuesday, Gonzalez was late covering first base on a fielders' choice ground out.
After the inning, television cameras caught Washington outfielder Jayson Werth and Gonzalez in a verbal altercation in the dugout. Gonzalez had to be screened by pitching coach Steve McCatty as Werth walked away.
"It stays between me and Werth," Gonzalez said.
Werth refused comment after the game.
"Just a little camaraderie going on," Johnson said. "Jayson sometimes can get a little vocal. He thought Gio was a little late covering first."
The Giants had evened the score after the rain delay ended because of a Desmond error at shortstop with runners at first and third in the fifth. Joaquin Arias scored that run.
San Francisco had scratched second baseman Marco Scutaro (stiff back), who was originally in the lineup. Arias replaced him and had three singles and a double for a career-high four hits and scored twice.
Desmond began the fourth with a double to right-center field. LaRoche followed with a single to right. Then Wilson Ramos hit a ball off Bumgarner's right knee. It deflected to third baseman Pablo Sandoval, who threw out Ramos as Desmond scored to put the Nationals up 1-0.
Gonzalez remained in the game despite the sore back, and kept San Francisco off the board. The Giants had runners at first and second in the fourth before Gonzalez struck out Brandon Crawford looking to end the threat.
That was the end of his night at 69 pitches. Thunderstorms moved in and halted the game at 8:28 p.m.
Kurt Suzuki added a run for Washington with a sacrifice fly in the eighth.
Harper didn't start the game because he had the flu, according to Johnson, but made a pinch-hitting appearance in the eighth inning.. San Francisco CF Angel Pagan, on the DL since May 28 following surgery on his left hamstring, could start a rehab assignment at the end of this week, Bochy said. ... Nationals RHP Ross Ohlendorf, on the DL with a right arm injury, was expected to throw a bullpen session Tuesday and will make a rehab start on Aug. 15 or 16, according to Johnson. ... Washington LHP Ross Detwiler, on the DL since July 4 with a herniated disc in his back, won't resume baseball activities for at least another week, but is expected to return this season, Nationals GM Mike Rizzo said. ... San Francisco starts RHP Tim Lincecum (6-11, 4.18) on Wednesday in the second of a three-game series. He faces Washington RHP Jordan Zimmermann (13-6, 3.06).