After stealing third, he trotted home when Freese connected on a 2-2 pitch, sending it deep into the left field bleachers for the Cards, who avoided their first three-game sweep at Wrigley Field since 2006.
Freese also contributed an RBI single while Shane Robinson went 3-for-4 in the victory.
Lance Lynn (4-0) won his fourth straight to begin the season, yielding only one run on six hits over eight innings while walking two and striking out seven.
Volstad let in four runs on six frames over a six-inning start for the Cubs.
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