ED. NOTE: Due to a lengthy rain delay, the Padres-Pirates game did not end by press-time.CHICAGO — Postseason or regular season, Daniel Murphy keeps crushing the ball at Wrigley Field.Murphy hit two home runs to back Tanner Roark, and the Washington Nationals won the opener of a series between division leaders by beating the Chicago Cubs 4-2 Friday.With the game-time temperature at 63, Murphy hit a two-run homer in the first and connected off Kyle Hendricks leading off the sixth for a 3-0 lead.Counting the postseason, Murphy is 20 for 38 with four home runs in his last 10 games at Wrigley.Roark (9-7) didn’t allow a run until a Javier Baez two-run homer in the seventh.