Michael Conforto hit a tiebreaking single that plated two runs in the eighth inning to lift the visiting San Francisco Giants to a 3-1 victory over the Pittsburgh Pirates.

Mike Yastrzemski hit a solo homer for the Giants, who have won four straight games.

San Francisco starter Alex Cobb gave up one run and four hits in six innings, with five strikeouts and two walks.

Taylor Rogers (5-3) pitched a scoreless seventh.

Camilo Doval pitched the ninth for his major-league-leading 28th save.

Henry Davis hit a solo homer for the Pirates, who are 2-9 in their past 11 games.

Pittsburgh starter Johan Oviedo, who has lost seven decisions in a row, allowed one hit -- Yastrzemski's homer -- over seven innings. He matched a career high with 10 strikeouts and issued three walks.

Carmen Mlodzinski (1-2) recorded one out and was charged with both eighth-inning runs. Only one was earned.

With one out in the second, Yastrzemski hit his 11th homer, to right, for a 1-0 San Francisco lead.

Pittsburgh came right back. On the first pitch of the bottom of the second, Davis hit his second homer, to left center, for a 1-1 tie.

The Giants had a scare in the fifth. Cobb, an All-Star, took a comebacker by Bryan Reynolds, but still managed to get the third out of the inning. The ball appeared to hit Cobb flush near his left ankle. He went down, bounced up quickly and walked off the field on his own. He received medical attention in the dugout and was able pitch one more inning.

In the eighth against Mlodzinski, LaMonte Wade Jr. drew a four-pitch walk and went to second on Joc Pederson's single to right. David Bednar relieved Mlodzinski and struck out J.D. Davis.

Conforto singled to right. Pinch runner Casey Schmitt scored and, when rookie second baseman Nick Gonzales took a cutoff throw but did not immediately throw home, Pederson also scored to make it 3-1.

There was a weather delay of about 40 minutes at the start of the game.

--Field Level Media