Buster Posey hit a go-ahead double as part of a three-run fifth inning and the San Francisco Giants held on to beat the Miami Marlins 6-4 on Thursday night.Miami Marlins' Garrett Jones rounds third base after hitting a two run homer against the San Francisco Giants during the second inning of a baseball game, Thursday, May 15, 2014, in San Francisco.San Francisco Giants' Hunter Pence is greeted in the dugout after scoring against the Miami Marlins during the fifth inning of a baseball game, Thursday, May 15, 2014, in San Francisco.San Francisco Giants' Michael Morse celebrates in the dugout after hitting a two-run home run against the Miami Marlins during the third inning of a baseball game, Thursday, May 15, 2014, in San Francisco.San Francisco Giants' Buster Posey hits a two RBI double against the Miami Marlins during the fifth inning of a baseball game, Thursday, May 15, 2014, in San Francisco.