Judy, for optimum results freeze your food quickly and thaw it slowly. That's how to prevent excess moisture loss in meat. Thawing in a microwave oven will cause increased moisture loss. It's better to plan ahead and thaw in your refrigerator.
Many cooks here have satisfactory SV outcomes starting from the frozen state.
Chicken breasts can be particularly delicious if packed and frozen with a little concentrated stock or wine, seasoning, and some herbs. It mostly contributes to aroma which is a significant part of taste.