Giants 2, Diamondbacks 0: Chad Gaudin allowed three hits over seven superb innings as host San Francisco won the opener of the three-game series.

Buster Posey and Hunter Pence each drove in a run in the first inning against Ian Kennedy (3-7), who remained winless in eight starts since June 1 despite yielding only two hits over the next five frames. The loss cut Arizona’s lead over second-place Los Angeles in the National League West to 1 1/2 games.

Gaudin (4-1) struck out eight without issuing a walk as he lowered his ERA to 2.23 in seven starts. Four relievers kept Arizona scoreless in the eighth before Sergio Romo worked a perfect ninth for his 22nd save in 25 opportunities.

Arizona, which has lost six of its last seven meetings with the Giants, loaded the bases with two outs in the eighth before Santiago Casilla retired All-Star Paul Goldschmidt on a grounder to shortstop to end the threat.

Pence and Brandon Belt had two hits apiece for the Giants, who have won four of their last five to move within 5 1/2 games of Arizona. San Francisco had just one extra-base hit after Posey’s first-inning double.

GAME NOTEBOOK: Gaudin has tossed 11 consecutive scoreless innings and allowed a total of two runs over his last four starts spanning 23 1/3 frames. … Arizona’s streak of games with an extra-base hit ended at 79, the longest such run in the majors this season. ... Romo has a 29-game scoreless streak against the Diamondbacks consisting of 21 2/3 innings.