I just thought of this. It's silly, i know, but i'm surprised it never comes up.
Why can't managers get the flu, or a virus? Or even a cold? I mean, you're around the players just as much as their teammates, right? Surely if you leave a player to the physio after getting a virus, the manager should have just as good a chance as anyone to catch it. And then you can decide whether you want to send yourself home, or leave yourself to the physio

. Or perhaps you are just sent home for a few days until the next matchday.