Casey Blake hit a tiebreaking two-run homer in the eighth inning and the Los Angeles Dodgers earned a 4-2 victory over the rival San Francisco Giants in the opener of a three-game set on Monday night.

With a full-count, Blake belted his eighth homer of the campaign off reliever Santiago Casilla (1-2), lifting the Dodgers a half-game ahead of the Giants for second place in the division and four games behind National League West leader San Diego.

Jeff Weaver (5-1) picked up the win with one inning of two-hit relief. With closer Jonathan Broxton getting the night off, Hong-Chih Kuo allowed runners on the corners in the ninth but got the final two outs for his second save.

Dodgers starter Chad Billingsley, coming off the disabled list with a strained right groin, allowed two runs on five hits in six innings, while Barry Zito gave up two runs on six hits in six innings with six strikeouts and two walks for the Giants.

Manny Ramirez went 3-for-3 with a third-inning RBI double that gave Los Angeles a 2-1 advantage. Freddy Sanchez tied things in the sixth with a single to center.