Arrieta pitched eight strong innings for his major league-leading 19th win, and Starlin Castro homered to lead the Chicago Cubs past the Philadelphia Phillies 5-1 in the first game of a doubleheader Friday night.
In the second game, Kyle Schwarber homered twice to lead the Cubs to a 7-3 win and a sweep of the doubleheader.
Arrieta (19-6) won his eighth straight start, allowing six hits with seven strikeouts and two walks to become the first Cubs pitcher to win that many in a row since Milt Pappas won 11 consecutive games in 1972.