San Francisco 3, Arizona 2

Giants 3, Diamondbacks 2: Buster Posey belted a two-run homer and Barry Zito pitched into the seventh inning as visiting San Francisco won its fourth straight game.

Zito (12-8) gave up one run over 6 2/3 innings for the Giants, who remained 7 1/2 games ahead of Los Angeles in the National League West after the Dodgers posted a 4-3 win over St. Louis late Saturday. Sergio Romo worked around a leadoff single in the ninth for his 11th save

Arizona fell 4 1/2 games behind St. Louis and Los Angeles in the race for the league’s second wild-card spot despite a strong outing from Wade Miley (15-10), who allowed three runs over seven frames.

Justin Upton forged a 1-1 tie in the bottom of the fourth with a two-out homer before Posey answered in the fifth with a two-run shot to right field.

Posey went 3-for-3 for the Giants, who have won 12 of their last 14 road games and are 23-7 away from home since July 17. With Posey starting at first base, catcher Hector Sanchez threw out two runners attempting to steal.

Arizona, which dropped to 2-8 in its last 10 games at Chase Field, cut into the Giants' lead in the eighth on Paul Goldschmidt’s two-out RBI single off Romo.

GAME NOTEBOOK: CF Angel Pagan led off the game with his 13th triple to set a new single-season San Francisco Giants record. … The Diamondbacks tied a franchise record by scoring four runs or less in their 12th straight home game. … San Francisco has won each of Zito’s last eight starts.

• Arizona will play their next game at home against San Francisco. The Diamondbacks have a W/L % of .514 after a win and .466 after a loss.
• San Francisco will play their next game on the road against Arizona. The Giants have a W/L % of .549 after a win and .603 after a loss.