Buster Posey began a string of three straight two-out doubles in the sixth inning, and Madison Bumgarner extended his streak of unbeaten starts to 10 Tuesday night as the host San Francisco Giants opened a two-game interleague series against the rival Oakland Athletics with a tense, 3-2 victory.

Scooter Gennett produced an insurance run with a sacrifice fly, and Will Smith survived a shaky ninth inning, helping the Giants reach .500 at 60-60 with a fourth win in the past five games.

Bumgarner (8-7) and A's left-hander Brett Anderson (10-8) locked horns in a scoreless pitchers' duel until Oakland's Stephen Piscotty belted a two-out, two-strike homer off the San Francisco ace for a 1-0 lead in the fifth inning.

The homer was Piscotty's 12th of the season.

The Giants bounced back to take the lead for good in the sixth when Posey, Evan Longoria and Kevin Pillar smacked consecutive doubles against Anderson, the latter pair each driving in a run for a 2-1 lead.

Bumgarner completed seven innings, allowing just the one run on two hits. He struck out nine and did not walk a batter.

Before he called it a night, Bumgarner contributed a sacrifice bunt in the seventh inning after A's reliever Jake Diekman walked Aramis Garcia and Brandon Crawford to open the inning.

When Gennett, batting as a pinch hitter, greeted Yusmeiro Petit with his sacrifice fly to center field, the Giants had a 3-1 advantage.

Anderson, who had been unbeaten in his previous seven road starts, was pulled after six innings, charged with two runs on six hits. He struck out four and, like Bumgarner, issued no walks.

Pillar finished with two hits for the Giants, who won for just the sixth time in their past 15 meetings with the A's dating back to 2016.

The A's finished with just five hits, two of which came against Smith to open the ninth with the Giants clinging to a 3-1 lead. When Matt Chapman added another single with one out, Oakland had the bases loaded.

The Giants closer struck out Matt Olson before walking Mark Canha to force in a run, allowing the A's to get within 3-2.

Smith then struck out Chad Pinder for his 29th save.

The A's have alternated losses and wins over their past eight games.

--Field Level Media