Offensive coordinator vs head coach

We all hear about how this coach is a “offensive guru” etc. For instance Kiffin etc.

Obviously coaches and coordinators are talking via headset throughout the game.

If something offensively goes well the guru head coach gets credit. If something is done poorly it’s attributed to the offensive coordinator.

How much percentage wise is the coordinator calling plays, head coach changing plays, qb changing plays at the line etc.

Last night I didn’t like the two qb draws called that got stuffed at the line in the Bama game. Evans was hurt, Judkins was gassed, do you think it’s the head coach or coordinator calling those?

Sometimes it seems the coordinator position is a fallback option to blame whether a D coord or O coord.

How can we really find out who is calling or adjusting plays and where blame truly lies?