If you're using the fridge, it will take around 12 hours to defrost.
Flip the breasts and defrost them for 1 more minute.
This means that you can avoid undercooked or overcooked chicken, and your guests will be more likely to enjoy their meal.
If people think about microwave defrosting, they generally have meat in mind.
Check after 1 minute to know the progress of the food.
One piece of chicken may thaw fairly quickly; several pieces of chicken may require more time, as electricity is split between pieces.