I’ve written before on how most coaches rate passes in serve reception and how they should relate to the desired outcome – a sideout. The question sometimes comes up whether we can do something similar for digging in defense.
Raw digs are not particularly indicative of performance for a team. I posted some stats which show that pretty demonstrably. For this reason, Mark Lebedew has proposed a new metric attacks per defensive opportunity (ATT/D). It’s at least a reasonable starting point when looking at team level defensive performance.
But what if we want to make individual level assessments – like comparing two liberos?
In that case, we have to consider a few things.
First, what is the desired outcome? As I suggested in What’s the objective of defense in volleyball?, it’s not simply to keep the ball off the floor. We want to be able to use it as the basis for a counter-attack. Thus, we have a similar sort of mentality as in reception. Higher quality digs lead to better attack possibilities, so we should rate digs in a way which reflects that.
Second, how do we count dig opportunities? We can’t calculate a dig rating only on dug balls. That might be fine when looking at the technical capability of the players. It doesn’t factor in, however, a situation where one player is simply able to get to more balls through being faster, reading better, etc. Thus, we really should be thinking in terms of balls in the area of responsibility of the players – one which should be similar for each. Plus, ideally we’re comparing them against similar attackers and behind a consistent block.
Third, we can’t rate on the basis of actual outcomes (e.g. kills). Those are reliant on other players. It’s fine to think that way when viewing the full team, but not at the individual level. We have to think, instead, on the basis of likely or expected outcomes. This is basically the same thing we do for serve receive.
Finally, how do you account for digs back over the net and digs that end up in free balls? You don’t want them to count the same as undug balls.
Something to ponder.