Jayson Werth hit his first homer in almost a month and drove in three runs, and the Washington Nationals capitalized on Matt Cain's erratic start to beat the San Francisco Giants 6-2 on Wednesday night for their fourth straight win.Washington Nationals pitcher Tanner Roark throws to the San Francisco Giants during the first inning of a baseball game, Wednesday, June 11, 2014, in San Francisco.Washington Nationals' Jason Werth (28) is greeted in the dugout after hitting a home run against the San Francisco Giants' during the fifth inning of a baseball game, Wednesday, June 11, 2014, in San Francisco.Washington Nationals' Adam LaRoche hits a two RBI single against the San Francisco Giants during the first inning of a baseball game, Wednesday, June 11, 2014, in San Francisco.Washington Nationals' Jason Werth hits a home run against the San Francisco Giants during the fifth inning of a baseball game, Wednesday, June 11, 2014, in San Francisco.