I don’t know why this never occurred to me before. so quarterbacks have headsets in their helmets so they can communicate with the coaching staff. I was always under the impression that they only used it before the play, just to prevent using a runner, but is the coach ever on the microphone during the play? maybe telling the quarterback where somebody is open if he can’t see it
Here’s a really good podcast episode that includes that question:
https://www.20k.org/episodes/blue42