Subtlety and Context in Interpreting Volleyball Stats

Over at the VolleyTalk discussion website, user “38 Skynyrd” started a topic the evening of December 15, after the Penn State-Stanford NCAA title match, about volleyball statistics. The initial salvo in the discussion essentially argued for more subtlety and context in interpreting volleyball statistics, given that:

“…absolute raw numbers in the box score do not always tell the true story of how good or bad a player did in a given game or match.”

The full set of messages is available here. A number of suggestions were made by the discussants for new statistics. Given the obvious relevance of this discussion for our mission here at VolleyMetrics, I have excerpted a number of these ideas (with the author of each one credited in parentheses). These are shown below:

“…a hitter may have hit for good numbers overall, but if they made 5-6 hitting errors at critical points in the match, then their overall hitting percentage may still look good in the box score, but they still had a crappy match.

There are also a lot of stats that aren't tracked in the box score. Missed blocking or defensive assignments, poor choices in out-of-system plays, crappy free ball passes. A blocker could not block a single ball during an entire match, yet that player's coach could praise her for having the most incredible blocking match of her career if she made every single blocking assignment and move correctly, and took away what she was assigned to take away, and the back row defenders end up with 300 digs” (38 Skynyrd)

“…a blocked attack is not the same error as an outright hitting error. And there's no way to tell what a "0" attack led to. Did it throw the opposition out of system or did it not stress them at all? Was that hitting error caused by the block?” ([R]uffda!)

“One of the easiest ways to stat an individual player's performance during a match is to assign a +1, 0, -1 scale to each touch that they get on a ball. For instance,

+1 = excellent pass
0 = marginal pass (i.e. passed to 10-foot line)
-1 = bad pass, aced or shank

+1 = kill
0 = ball kept in play by opponent
-1 = hitting error (blocked, out-of-bounds, into net)

If [you] grade each touch a player makes [and average the scores], by the end of the match you'll have a score that is between -1.0 and +1.0.

It can help judge an individual players performance better, but it's not weighted for situational dynamics (i.e. a +1 contact when the score is 0-0 should not be weighted the same as a -1 contact when the team is down 23-29). It also doesn't address bad plays when the player is not touching the ball - such as out-of-position on defense, missed blocking reads, getting in another player's way on the court, etc.” (38 Skynyrd)

“…there are still important many areas of play which are not covered in the stats for volleyball. IMO [In my opinion], the most important of these are passes which do not hit the target, missed blocking assignments (i.e., failure to close the block) and missed digs in the back row” (Traveler5)

“One stat that is completely objective and I think could be useful would be what % of a player’s attacks are handled and then killed for a point by the other team. So if the other team digs your attack, and winds up getting a kill on that 3-touch sequence immediately following your attack, that would count negative, and if they don’t score, either by sending over a freeball or having a legit attack dug up, it counts towards you…

You could also… break down how many blockers were on each of a player’s attacks, and how well they hit against 0, 1, 2, and 3 blockers. This could also be used by setters to see the average number of blockers their hitters had to go against.

Front row vs. back row would also be nice, since a player good enough to get a lot of back row swings is probably going to hurt their % some since that is a lower percentage shot” (Chance)

Suggestions for refinements of dig statistics: “…opportunities matter. Thus, I have calculated the "dig %", which is digs/non-error attacks (it doesn't make sense to penalize a team for not digging a ball that is blocked or out)… [and] digging compared to opponents… difference between digs and opponents’ ” (p-dub)

I and another user, Mike Garrison, both alluded to improvements in baseball statistics that have been fueled by the “sabermetric” movement. Some responses:

“Baseball is helped by the fact that it is such a discrete game. You are either out or safe. You are either at first, second, or third base. A pitch is either a ball or a strike. Etc.

The weakest part of SABRmetrics is the fielding stats… A player can just barely miss a ball or not really come close to it at all…

Most other sports, including volleyball, are more like baseball fielding than hitting or pitching. So I would start by looking more at fielding stat methods than at hitting or pitching methods.” (Mike Garrison)

“Even more important is the independence of events. Whereas the events in baseball are not completely independent, they are far closer than any sport. If a batter is batting with a runner on first, you generally know where that runner is going to be at any time... None of this can be said for volleyball (or most other team sports). Players are all over the place, and offensive sets can vary significantly.

The best example of baseball's stats independence is in offense and defense. Baseball (and like sports) is the only sport where a great defensive play does not improve offensive opportunities. In all other sports, the defense can help the offense. In volleyball, great defense can slow the opponents attack, and we always hear about "transitioning." Shoot, the defense can even score directly on a block...” (p-dub)

“[Unlike baseball, where the pitching rubber and batter’s box constrain the positions of the key players...] Volleyball is a game where the ball is struck from almost anywhere on the court, and there isn't enough information available…

My biggest pet peeve of the [n]umber crunchers are those who tout ridiculous stats or won-loss records without regard for the average competition faced” (Bear Clause)

Where feasible, I will consider gathering the data to produce the statistics suggested above. I invite you readers to do the same!