Giants 5, Diamondbacks 4: Brandon Belt hit a walk-off single to score Andres Torres from second base and host San Francisco rallied to extend its winning streak to four games.

After Buster Posey tied the score in the eighth with a two-run homer off David Hernandez, the Giants opened the ninth with Torres’ single off Tony Sipp (1-1). Torres moved to second on Brandon Crawford’s sacrifice before scoring easily on Belt’s single to left field.

Sergio Romo (1-1) recorded one out in the eighth for the win for San Francisco, which improved to 9-1 against National League West opponents. The Giants’ comeback spoiled a strong outing by Arizona starter Wade Miley, who allowed two runs while striking out seven over 6 2/3 innings.

Miley also belted his first career homer leading off the fifth inning to break a 2-2 tie and Eric Chavez added to the lead with a one-out homer in the sixth. Both homers came off Giants starter Ryan Vogelsong, who gave up four runs on seven hits over seven frames.

Cody Ross gave Arizona an early lead with his two-run single in the first, and San Francisco quickly tied the score with RBI doubles from Pablo Sandoval and Posey in the bottom half of the inning.

GAME NOTEBOOK: The Giants have won 17 of their last 21 home games dating to last season. …Miley’s homer was the first base hit by a Diamondbacks pitcher this season. … The Giants have allowed three home runs to pitchers in a month for the first time since June 1953.