The win improves the Giants to 7-15 away from San Francisco. They have won six of seven overall.
The Cardinals dropped their third straight and fourth of six. It's their fourth three-game skid of the season.Bryan Morris (2-0) pitched a perfect eighth inning, striking out two, to pick up the victory. Mark Melancon earned his seventh save.
The Giants scored twice off Cardinals closer Seung Hwan Oh (0-2) in the ninth to take the lead. It was Oh's second blown save of the year.Brandon Belt and Brandon Crawford singled ahead of Nunez, who hit his 10th double of the season to left center.
