Hasn't happened yet, but.......

[ajmc]

"as inconspicuously as possible". Stopping the game and talking to the coach near his sideline, with your back to the bench area, in a tone keeping the discussion private seems to fit, "as inconspicuously as possible" to me.

Conspicuous would be shouting towards the sideline from the middle of the field, or facing the team area and loudly balling out the coach in front of his players, or shouting and gesturing while you were talking to him. His talking to his players confirmed to, "everyone on that sideline knew why I was there".

Sometimes you just have to crack a few eggs to make breakfast, but you should avoid throwing the shells in anyone's face.