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.
In this sentence, the use of commas creates confusion due to the repeated phrases that describe each captain's position. Using semicolons would clarify the separation of examples:
The captains of the high-school softball team are pitcher; Marisa Martino; outfielder; Rachel Morrison; and catcher; Lisa Fiore.
(Note: To be perfectly correct, you might also consider reconstructing the sentence to avoid this confusion without needing semicolons, for example: "The captains of the high-school softball team are Marisa Martino, the pitcher; Rachel Morrison, the outfielder; and Lisa Fiore, the catcher.")