In American football, on read-option plays, how does the RB know when to fully grasp the ball and when not to because the QB "pulls" the ball?
Commentators praise the QB on plays where he sticks the ball in the belly of the RB, only to pull the ball at the very last second and keeps it for a huge gain. In slow motion, it really looks like the ball is in the stomach of the RB with the RB's hands almost around the ball when the QB pulls it.
They have also blamed the QB/RB when there's a fumble because of miscommunication due to:
- the QB deciding to handoff the ball but the RB doesn't grasp the ball and it gets fumbled away or
- the QB tries to pull the ball but the RB has already fully grasped the ball and the ball gets knocked/pulled out by the QB and is fumbled.
I know teams who run a read-option offense probably practice these plays a lot so they "know", but as a layman, I'd like to know how the RB "knows" what the QB is going to do. Does the QB bark some code word before handing/keeping the ball or they both "know" because they both read the DE and know what the other is going to do and the fumbles are just unfortunate mistakes?