Starlin Castro hit a three-run homer in the sixth inning to break open a tight game as the Cubs beat the Pirates, 7-4. Castro also had an RBI single for Chicago, which built an early 4-0 lead and led the rest of the way in the opener of a four-game set at Wrigley Field. Andrew McCutchen smacked his 27th home run for Pittsburgh, which closed to within 4-3 before Castro's blast put the game away. Chris Rusin pitched five innings of two-run ball for the win and Carlos Marmol notched his 20th save. James McDonald fell to 12-and-8 with the loss. The Bucs have lost seven straight.