I know it's common for many managers to have the same player do the placekicking and the punting.
But is it illegal to have juste one gunner? One kick returner? One special cornerback?
In other words, do we absolutely have to put two players in both of these special team position?
One on the right, the other to the left?
The game requires 2 of each of those positions. If you don't put anybody there, it will randomly select someone from your roster to fill the spot. There is a small bit of intelligence used when players are randomly selected for these positions. Obviously, the same player won't be used in both positions. Also, nobody assigned to K or P will/can be used as a gunner, and nobody can be assigned to both special team cornerback and kick returner. Other than that, anything else goes.