Curt Casali, Darin Ruf and Wilmer Flores hit home runs and five relievers combined to shut out the Washington Nationals over the final five innings Friday night as the host San Francisco Giants opened a three-game series with a 5-3 victory.

The Giants used two double plays, one to end the eighth inning after the Nationals had loaded the bases, en route to their National League-leading 55th win of the first half.

Casali hit a two-run homer in the second before Ruf had a solo shot in the fifth and Flores hit a solo homer in the seventh. The Giants lead the major leagues with 130 homers.

The long balls were the third of the season for Casali and the ninth apiece for Ruf and Flores, accounting for all the San Francisco scoring after Ruf singled in Mike Yastrzemski to get the Giants on top in the last of the first.

Washington backup catcher Tres Barrera drove in a pair with a triple, his first career extra-base hit, and scored on Gerardo Parra's double in a three-run fourth.

While Ruf's homer was giving the Giants the lead and Flores' blast was extending it, San Francisco relievers Jarlin Garcia (1-2), Zack Littell, Dominic Leone, Tyler Rogers and Jake McGee combined to throw one scoreless inning apiece.

Garcia, who pitched a scoreless fifth inning, was credited with the win. McGee, who worked out of a two-on, two-out jam in the ninth, got his 18th save.

Sam Clay (0-3), who surrendered Ruf's homer, took the loss.

Neither starter got a decision.

Giants right-hander Logan Webb, activated before the game after a second stint on the injured list due to shoulder soreness, was pulled after 45 pitches. He threw three shutout innings, allowing one hit and no walks with four strikeouts.

Nationals righty Paolo Espino was charged with San Francisco's first three runs on six hits in 3 2/3 innings. He walked one and struck out one.

Casali had three hits and Ruf two for the Giants, who split a four-game set in Washington earlier this season.

Barrera, who replaced Yan Gomes (oblique) in the second inning, collected two hits for the Nationals, as did Trea Turner and Starlin Castro.

Washington out-hit San Francisco 11-10.

--Field Level Media