The Pittsburgh Pirates scored three seventh-inning runs without the benefit of a hit to break a tie en route to a 6-4 victory over the host San Francisco Giants in the opener of a three-game series on Friday night. After the Giants had used home runs by Steven Duggar and Alex Dickerson to erase a 3-0 deficit, the Pirates pieced together three walks and two infield grounders for their go-ahead rally in the seventh to snap a four-game losing streak.