The Cardinals' closer Seung-hwan Oh could not close out the game for his team Friday night.
Oh allowed a leadoff single to Brandon Belt and then two batters later another single to Brandon Crawford. The following batter, left fielder Eduardo Nunez, doubled to center field to bring home both runners and give the Giants a 6-5 lead.
Friday was Oh's second blown save of the season, with the first coming on opening night.
Tuivailala allows run in eighth, Giants cut Cards' lead to 5-4
Sam Tuivailala allowed three singles in two-thirds of an inning to give the Giants their fourth run of the night.