Giants 6, Diamondbacks 2: Hunter Pence belted his third career grand slam and Matt Cain matched his career high in wins as visiting San Francisco held off Arizona in the opener of the three-game series.

Pence hit a liner over the left-center field wall with one out in the third inning off Tyler Skaggs (1-2) for his first grand slam since 2008. The Giants lead the National League West by 7 1/2 games over the Los Angeles Dodgers.

Cain (14-5) gave up one run on four hits and five walks over five innings and moved to 8-1 over his last 14 road starts. The Diamondbacks were 2-for-16 with runners in scoring position and left 15 runners on base.

Arizona, which dropped 11 games out of first in the NL West, cut into the Giants lead in the bottom of the sixth on Chris Johnson’s RBI single. The Giants escaped further damage when Jeremy Affeldt struck out Aaron Hill with two runners on to end the inning.

Pablo Sandoval broke out of a 2-for-23 slump with three hits for San Francisco, which has won 11 of its last 16 games. Giants reliever Santiago Casilla drove in a run with his first career hit in the eighth.

GAME NOTEBOOK: The Giants improved to an NL-best 22-7 in road games since the All-Star break. … Arizona closer J.J. Putz was available after missing the last two games with a stiff back. … Skaggs was pulled after giving up five runs over four frames.