From the Team Dashboard

You can instantly identify available and unavailable athletes by looking at the Health column of the team dashboard (red=unavailable due to health problem; yellow=available with limitations; green=available).

From the Team Charts

The Health Problems section automatically displays all the athletes with health problems.

Availability Statistics

To generate a graph that displays the number of percent of available/unavailable athletes over time, open Team Charts, select a period, and scroll down to the Availability section