In my Volleyball player efficiency ratings post I referred to a short paper proposing a way to evaluate setting. That paper is A Reconceptualisation of Traditional Volleyball Statistics to Provide a Coaching Tool for Setting by Alexis Lebedew. The paper’s basic idea is to combine a pass/dig rating (like the kind mentioned here) with a 0-3 rating for the outcome of a spike to get a set rating (0 for error, 3 for kill). The pass rating is effectively inverted. Good results off poor passes are rated higher than ones off good passes. This accounts for set decision and/or execution.
Conceptually, I like the idea proposed by the paper. There are a couple of issues with this particular ranking process, though.
No real new information
The set rating system was evaluated to see if it related to the probability of winning a set. It does, but that’s no real surprise since it is heavily influenced by outcomes. Specifically, with the highest ratings coming on kills. We already know that getting a lot of kills generally results in more winning. We also know that both hitting efficiency and pass quality relate to scoring points and winning sets. As a result, we don’t really have any additional information from this rating in that context.
Hitter skill is a major factor in attacking outcomes. Good hitters can make up for poor sets. Poor hitters, though, struggle even with great sets. Further, the quality of the block and defense the hitters face is a meaningful factor in attack outcomes. As such, it is problematic to compare setting across teams. A great setter on a poor team simply won’t rate as well as a setter on a good team.
So what to do
If the underlying idea of rating sets is to be able to compare setters directly then I fully support factoring in pass quality. It is the primary control variable determining what can be done with any given setting opportunity. Including it allows us to look at setting on an even playing field.
In order to really assess the quality of sets, though, we need to also be controlling for the outcomes in a similar way we do for passing. If a passer puts up a perfect pass, we don’t punish them because the setter mishandled the ball, nor do we bump up their pass rating because the setter was able to put up a good set off a poor pass. I think we end up circling back to the idea of rating sets similarly to how we rate passes. The problem, though, is we really should be factoring in play calling and decision making in the process, which is no easy thing.
All that said, though, I do think the type of set rating proposed in the paper could be useful in comparing setters on the same team or in a situation where teams and players are quite similar in level of play. In that case, hitting quality and the block/defense of the opposition would presumably be the same for each, allowing for a level assessment.