Both players felt ill and were scratched from Sunday's game. Moustakas was placed on the injured list, but he was activated Wednesday with catcher Tyler Stephenson being optioned.
Teammate Matt Davidson was placed on the injured list Saturday after testing positive for COVID-19.
Manager David Bell said that Moustakas didn't feel well when he woke up Sunday morning and was told to stay home as a precaution.
The Associated Press contributed to this report.