Seeing the shortstop smoke a pair of line-drive two-baggers was a welcome sight for Cubs fans.
In July, Castro carried a .170 batting average and .194 on-base percentage. That batting average is the second-lowest monthly mark he's ever posted, and the on-base percentage was the worst of his career.
However, memories of that ineffectiveness were put out of mind early Tuesday evening.
In the third inning, Castro patiently worked a 3-1 count and jumped on J.A. Happ's 92-mph two-seam fastball, shooting it out to right-center and plating Anthony Rizzo to give the Cubs a 2-0 lead.
He followed that up in the fifth inning by driving the first pitch he saw from Pirates reliever Jared Hughes, a 93-mph sinker, to left field for his second double, scoring Rizzo once again and lifting the Cubs to a 4-0 advantage.
Statistically, Tuesday night was a revelation for Castro, who had only one multihit performance in his previous 25 games. Over that span, he was 13-for-91 (.143).
His two-double showing was also just his second game with more than one extra-base hit this season. The other was on May 12 against the Mets.
Despite prior struggles, Cubs manager Joe Maddon is confident in Castro's continued development.
"He's had a nice history of Augusts," Maddon said. "Everybody's going to look at his batting average, and I understand that, but he's close to 50 RBIs right now. He's got some really big hits for us.
"I still look at his birth certificate. The guy's 25. Starlin has a lot left to learn."
Perhaps Tuesday night will be yet another building block.
John McGonigal is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.