Carlos Gonzalez looped a two-out, two-strike, two-run single to center field in the 12th inning Thursday night, delivering the visiting Colorado Rockies a 5-3 win over the San Francisco Giants in the opener of a four-game series. The Giants fell despite first baseman Brandon Belt hitting a home run for the fourth consecutive game, a two-run shot that tied the game at 3-3 in the sixth inning. Neither team scored again until Chris Iannetta and Charlie Blackmon drew consecutive one-out walks off the sixth Giants pitcher, Pierce Johnson (2-2), in the 12th.