Malo, a 22-year-old infielder, hit his shot with two outs in the eighth inning, snapping a 3-3 tie.
A 48th round pick in the 2003 draft from Northeastern Oklahoma A&M, Malo - a Quebec native - batted .239 with seven home runs and 33 RBI in 91 games for St. Lucie this year. He also played 20 games at Class-A Brooklyn of the New York Penn League.
The Cardinals made a comeback attempt against St. Lucie closer Carlos Muniz in the top of the ninth inning, with Joe Mather cracking a two-run home run.
Muniz came back to strike out Luis Cotto for the final out, completing an inning in which he struck out three batters.
Gary Carter's St. Lucie Mets club won a first half Florida State League division title and finished second to Palm Beach in the second half, posting a 37-32 record.
The Mets won Game 1 of the best-of-three series on Tuesday as right-hander Jose Sanchez held Palm Beach to one run and two hits over six innings, leading to a 6-4 victory.
St. Lucie will now continue on to play the winner of the FSL West series between the Fort Myers Miracle and the Dunedin Blue Jays on Friday. The series is tied at 1-1 with a deciding game scheduled for Thursday.