Buster Posey and Wilmer Flores hit back-to-back homers in the first inning, Thairo Estrada had a key double in the seventh and the San Francisco Giants defeated the Los Angeles Dodgers 7-2 in the opener of a pivotal four-game series between the NL West rivals. Posey had two hits and drove in two runs in his first game back after he missed two weeks due to a bruised left thumb. Estrada — who is taking over at shortstop after All-Star Brandon Crawford was placed on the injured list due to a strained oblique — came through with a two-run double in the seventh inning as the Giants broke open a close game by scoring four times.