Russell McElroy, Hondo HS in Hondo, TX.
Back Row Defense
Typically a person's head and their vision does not transfer quick enough to see the hit and then follow the ball to the point of block and find that they are ready to dig up the blocked ball.
So when training players to cover a back row attacking hitter, I have the coverage players watching the attacker to the point of being able to communicate that they are clearly jumping from behind the 10' attack line.
Then, at the moment of the jump, the covering players must be in a low ready defensive body position with their platform extended, and at the same moment, train their eyes on the blockers at the net instead of watching and following the ball.