The sentence that requires semicolons instead of commas is:
The captains of the high-school softball team are pitcher, Marisa Martino, outfielder, Rachel Morrison, and catcher, Lisa Fiore.
This sentence contains multiple items in a list where each item includes a description and a name, making it appropriate to use semicolons to separate them for clarity:
The captains of the high-school softball team are pitcher: Marisa Martino; outfielder: Rachel Morrison; and catcher: Lisa Fiore.