But if you simply change may to must then it can be read in a way that guarantees that the player misses at least one drive after the one in which he is KOd. After all you roll when you set up for the next drive and he must go in reserves at that time not on the pitch.
I think that you are reading too much into the "may". It is simply proper grammar. Players should be returned to the field, whether or not the coach wants it to happen.
Tell him to stop being a wuss!
Spazz