Tag Archive for volleyball statistics

The importance of different skills in volleyball

There’s an academic paper worth having a look at titled Skill Importance in Women’s Volleyball. Based on analysis of data from the 2006 BYU Women’s team, it looks at most of volleyball’s primary skills. I got hold of it as part of the discussion surrounding the It’s best to set the ball tight post. It also came up in the discussion of defense around the What’s the objective of defense in volleyball? post. This analysis is apparently the basis for the USA teams favoring sets off the net, and passes as well.

Be warned, the paper is academic, so it’s quite technical in many ways. One of the more interesting aspects of it is the list of references. It includes several evaluations of skills from different competitions.

It is important to understand that academic analysis of this nature can be quite reliant on the involved methodologies. Further, how the researcher collects and prepares the data is important. I should know. After all, I worked on just that sort of thing for my PhD. Also, this study includes only one team in one season. As such, it may be picking up things which are specific to that squad (idiosyncratic).

Short-coming aside, it is always good to understand the parts of the game which are the most important in your team’s success. That’s part of what motivated studies like this one and this one.

Hitter attack angles

Mark Lebedew once wrote on the subject of when hitters make the decision as to their angle of attack. That is whether they go line or cross with their swing. The post was a follow-up to a poll he ran asking when people thought hitters made their choice: before the set. When he sees the block starting position? When he sees the set? Perhaps when he sees the blockers’ hands? Or at some other point? Basically half of respondents said when they see the hands.

Mark’s view is that mechanically there’s not much chance of a hitter truly being able to set themselves up to hit with power both line and cross such that they could decide between the two in the last instant. I would contend that when the decision is made depends a great deal on the talent level of the hitter (leaving aside the question of the set for the moment). At the low end, hitters probably make the decision before the play even starts. I know this first-hand from working with them! At the upper end, vision and experience tends to allow for later decision-making.

At the 2015 HP Coaches Clinic there was a session which nominally was about scouting, but ended up being focused on training hitters to be able to hit multiple angles. Hitter attack angles were defined as:

Straight: In line with approach
Hard-Cross: Attack with a cross-body arm swing
Straight-Cross: Midway between Straight and Hard-Cross
Hard-Away: Aggressive wrist-away attack
Straight-Away: Midway between Straight and Hard-Away

It is important to note that these attack angles are all relative to the approach of the hitter. If, for example, we’re talking about an OH with about a 45-degree approach, then the straight attack would be on that 45-degree line. Hard-Cross would be the line swing. Hard-Away would be a sharp cross-court attack. The two mixed attacks would be in between, as shown here:
Here’s what it would look like for an OPP with a straight approach. Notice how the hard away shot is actually out of bounds. Clearly, that shot isn’t available. The straight-away shot might not be either.
AttackAngles2Obviously, the exact angles of these swings are going to vary from hitter to hitter. Some attackers will be able to hit more radical “cross” or “away” shots than others. I’ll share some of the training exercises they presented in the not too distant future.

Returning to Mark’s view, we had a conversation about it once when I visited him in Berlin. I personally, as a hitter, was a late decider in that I looked for the block, but I was very much a straight to hard away hitter, at least as an OH. Didn’t really have much of a cross-body swing from that side. I could mix one in from the right on occasion.

The point I made with Mark was that in theory a hitter can leave the decision right up to the point of elbow extension. That’s when they decide where on the ball to strike. But at what point do you start calling those angle shifts shots rather than full attacks, and can those angles really provide the same full range as going cross-body?

Serve first or receive first?

Your team wins the pre-match coin toss. Do you take serve? Or do you take receive?

At the upper levels of the sport the answer is very simple. You take receive. Why? Two reasons.

First, the sideout percentages are quite high for top level teams. Mark Lebedew shared some stats from the German men’s Bundesliga (top league) a while back which indicated that teams scored just about 2/3rds of the time when receiving serve. He’s since also provided data from Poland, France, Italy, and Russia. So from the perspective of getting on the board first, you don’t want to be serving.

Second, as Mark points out, the receiving team actually has less to do to win a set than the serving team:

“…in any given set, the number or sideouts is equal, give or take one.  What decides the set is the number of points the teams win on serve. The receiving team must win one more point on serve than its opponent to win the set. The serving team must win two more points on serve to win the set. Scoring a point on serve is more difficult than winning a point on reception. Therefore the team receiving first has an advantage.”

Of course the considerations are quite a bit different at the other end of the talent spectrum. There serving is much more dominant. If you’re coaching at a level where the sideout percentage is only about 1 in 3, then you’re going to want to have the first serve. The frequency at which points are scored on serve will tend to make what Mark outlines above irrelevant.

If you’re coaching in the middling zone where sideout rates are close to 50%, then other considerations may come into play.

Regardless, this is one area of coaching where knowing the relevant statistics can make for quite clear-cut decision-making. Of course, this might also tie in with how you decide your starting rotation.

Coaching Log – Sep 24, 2014

This is an entry in my volleyball coaching log for 2014-15.

This was the first official team training of the new season after final cut-down was made on Tuesday. The main idea was to set the overall tone of expectations for training and how I want the team to play.

I actually already started that on Monday and Tuesday in terms of being on time and what happens at the start of the session while the net is being put up. I expect those not involved to ball-handle lightly or do other volleyball-related activities until we’re good to go – not just stand around watching and chatting. They were told about how we had to institute consequences for tardiness last season and how I hoped that would not have to be the case this year.

Additionally, on Tuesday I introduced them to my balls-don’t-drop stance. That was something I wanted to reinforce at the start of training.

The key thing I was looking to start to develop, though, was the “gym as a safe environment” philosophy. By that I mean we are all supportive of each other and we are accepting of making mistakes – both our own and others – as part of the learning and development process. And not only do we support our teammates, but we accept support from them.

In terms of the volleyball, there were a couple of things I wanted to focus on:

1) Serving technique – This is mainly for the B team group where specific training is likely required to get them using consistent mechanics, but even with some of the A team players there may be an issue here or there.

2) Start to identify likely primary passers – This is mainly for the A team group as they will be the first to start competing (first SWVA in 2.5 weeks, then BUCS in 3 weeks). For this I wanted to do some statting of serve reception.

3) Evaluate blocking – I wanted to take a look at footwork and the other mechanical elements to see where work needs to be done.

Here was the plan:

– Blocking footwork patterns along the net as initial warm-up
Passing triplets and quads as a continued warm-up
– Target serving (zones 1, 5, and short)
– Get two serving and passing
– Game play

Unfortunately (or fortunately, depending in your perspective), three of the players were not dressed and ready to go on-time, so training started off with consequences. These players were 5 minutes tardy in being ready to go, so we did 5 sets of 4 (4 length of court sprints). Last year we did stuff at the end of training (not sprints, generally), but because this was the first day I wanted to reinforce the “be on time and ready to go” immediately – as well as the fact that it impacted the team, not just the individual.

Following the sprints, to let them catch their breath, I talked with them about the stuff I mentioned above. I told them about the positive gym atmosphere. I talked about how pushing themselves helps push the team forward, and mentioned the way improvements in last year’s team along the way made for increasingly competitive and intense training sessions as the season progressed.

After the talk, I had them do blocking footwork along the net – first single step shuffle, then the step-crossover-hop move. A fair bit of work will need to be done with especially the B-team players to make those patterns automatic. The blocking technique itself wasn’t horrible, though we don’t have any particularly big blockers.

I had them first do the passing triplets/quads. They started with overhand throws to act as an initial shoulder warm-up and to simulate a float serve with more control than we were likely to have if they simply served to start. After I think two rotations through, I did then have them go to short serves (meaning from inside the court, not that they served the ball short). This allowed me to observe common issues to address with the group, and to focus on certain things with individual players.

From there I had them do target serving. They had to put 5 balls in each of deep zones 1 and 5, and if they did that, to serve short. Again, I used the opportunity to do some individual player corrections.

After that it was the team serving and passing. Unfortunately, several balls dropped, so the team had to face the consequences (immediate set of 4). I had the players keep track of their passes so we could mark down each time through how many good out of how many total. In this case, I defined good as middle third of the court in front of the 3m line, so it wasn’t about perfect balls. Predictably, some players struggled. Others did quite well.

I finished up by having them play narrow court (about 2/3 width) Winners 4s. There was some ugly stuff, of course, but the captain told me afterwards she was pretty pleased with how competitive the players were. Along the way I reinforced both the value of taking risks and the need to communicate – particularly hitter availability when out-of-system.

Overall, not a bad session and not a great session. It was probably about what I expected. I’ve decided that at least for a while I want to have the A team players doing serving & passing together because the B team players were clearly struggling with some of the strong serves a couple of A team players have. I want to slow things down a bit for the B team players to let them focus on their technique a bit more and gain some confidence. They will still get to face the tougher serves at times in game-play situations.

We have out next training session tonight – 90 minutes in the big gym.

How important is blocking?

There’s a forum thread at Volley Talk on the subject of the influence of blocking on results. A blog post which suggests blocking may not be that important motivated it. Specifically, blocking is said to be the facet of the game least correlated to wins and losses. The post offers the 2012 University of Oregon women’s team as a prime example. That team played in the NCAA Division I national championship game, but actually was at or near the bottom of the Pac-12 conference in blocks per set during the regular season. Clearly, blocking isn’t all that important!

Are you convinced?

This manner of thinking reminds me of other potential misuses of data.

Blocking is not just about blocks

Of course the big issue with this discussion is that blocking isn’t just about blocks which score points. It is also about forcing hitters to change shots. It’s about funneling balls toward our best defenders. And it’s especially about slowing down hard hit balls. Unfortunately, it’s quite hard to objectively measure those sorts of things directly with standard statistics. We can only get there indirectly by looking at opponent hitting percentages and things like that.

What we can do, though, is ask the question what would happen if we don’t block at all. Once one reaches a sufficiently high level where attacking players hit hard and/or accurately enough to overwhelm the defense it clearly becomes the case that blocking is very important. Even a weak block is generally better than no block at all from this point onward.

Blocking because that’s what you’re supposed to do

That said, below that point where offense overwhelms defense in the absence of a block, it is quite legitimate to ask whether blocking is worthwhile. We as coaches – and by extension our players – often get caught up in the feeling like we have to do things a certain way regardless of the situation. This is another element of the discussion in Using 2-touch games to challenge your players in terms of being able to be effective vs. doing things the “right” way.

How often do you see double blocks put up against teams with no strong hitters? How many times do your own teams do it? I am certainly guilty of that. In all honesty, in part I let it be because I see a risk in making things more confusing for the players if I tell them to only single block or to not block at all. Of course, that just means I should train them to deal with that situation.

So at what point do we want players blocking – singly or doubly (or triply)? Should we always have players block in a developmental context?

Considering a set rating system

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

There was an evaluation of set rating system to see if it related to the probability of winning a set. It does, but that’s no real surprise since outcomes heavily influence the ratings. Specifically, the highest ratings coming on kills. We already know that getting lots 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 new information from this rating in that context.

Problematic comparisons

Hitter skill is a major factor in attack 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 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.

Volleyball player efficiency ratings

A while back I came upon a 3-part series of blog posts. It conceptualizes a unified way of looking at volleyball statistics across all categories. It’s dubbed the Volleyball Player Efficiency Rating by its creator. The three installations are here, here, and here respectively. The second refers to a paper on setter-specific ratings I address separately in another post. A number of folks came up with different variations on the player efficiency theme in the recent years.They are interesting conceptual exercises. At least the stat geek side of me thinks so!

When I coached at Brown I even developed one myself. I dubbed it the Point Contribution Ratio. Basically, I took the basic match stats for kills, blocks, digs, and assists. I then added in the 0-3 ranking we did for serve reception and the 0-5 score we used for serving into the mix. I weighted each stat based on how directly it contributed to points scored or conceded. The calculation looked something like this.

PCR = Kills + Blocks + Aces + 0.5 x Assists + 0.5 x 3-passes + 0.25 x 2-passes + 0.5 x 4-serves + 0.25 x 3-serves – Hitting Errors – Service Errors – Ball-Handling Errors – Block Errors

That’s not exactly it, but I think you probably get the idea. I made the comparisons on a positional basis because of the way different positions scored. Setters, for example, had the highest PCR because of their assists.

I never did actually test the PCR out statistically, though. That means I can’t give you an idea of how useful it might have been given the right weightings. Therein lies the problem with many of these volleyball statistical measures. We don’t know if they are meaningful when it comes to winning and losing points and matches. Jim Coleman actually did the statistical work on passing. He showed that how a team passed on the 0-3 scale related to their probability of scoring points (see his chapter in The Volleyball Coaching Bible). Those who propose new statting methods must do the same. Those who use statistical techniques to evaluate teams and players need to know that they actually have a measurable relationship to what we’re using them for. They can’t just sound good. Otherwise, we’re just spinning our wheels to no real purpose.

Where do your team’s points come from?

In his book, Thinking Volleyball, author Mike Hebert offers up a typical scoring chart for his college teams based on winning a 25-point set. It looked like this:

Kills 12
Opponent Errors 8
Terminal Blocks 2.5
Service Aces 2.5

I only share the specific numbers above as an example. It should not be taken as indicative of where your team should be in its point scoring distribution. These numbers are from upper level women’s NCAA Division I play. A typical distribution for teams at other levels, and on the men’s side, could vary considerably. For example, at lower levels of play I’d expect to see the influence of kills and blocks reduced. Similarly, errors and aces likely would be higher.

The point isn’t the specific numbers above, but the idea behind them. As coaches, we should have a good handle on how we score points and how we give them up. That allows us to set training priorities and develop match strategies. Additionally, if we know the point scoring balance of our leading competitors, we can get some sense of where our team needs to be, if it isn’t there already.

For example, going into the 2013-14 season I knew the women’s university team I coached needed to get stronger in the attack. In 2012-13 we could defend with just about anyone and keep our errors down. We just couldn’t get as many kills as we needed to compete at the top level. Recognizing that, from the very start of 2013-14 I focused on a more aggressive attack. We were never a dominant offense. We improved enough, though, within the scope of our overall play to reach the national semifinals.

Caution in thinking about these numbers is required, though. It’s easy to look at the table above and think something like “Well blocks and aces don’t account for very many points, so we should focus our time elsewhere.” The problem with that kind of mindset, though, is that while blocking and serving may not directly translate into a lot of points, they both contribute to them indirectly by putting the opposition under pressure, forcing mistakes or easier transition opportunities. So don’t just think all you need to do is work on hitting!

Player-centric volleyball stat collecting

In an issue of the AVCA’s Coaching Volleyball magazine there was an article on the collection and use of stats. It’s a pretty comprehensive discussion. It focuses, however, on the more basic stats, not the higher end stuff that some coaches use these days. The author takes the perspective of a coach in a small program where there isn’t much in the way of help for collecting stats during training, etc.

That article made me think about making the stat collection process more player-centric.

I wrote before about player-centric drills, which in contrast to coach-centric ones put players in charge of initiating the process. For example, a passing drill where players serve is player-centric. One where the coach serves is coach-centric.

So how can we take coaches out of the stat-taking process? Basically, players must keep track of serves, passes, hits, or whatever. This is in place of a coach (or manager) doing so. The article mentions doing something like having passers write down how they did in a serve receive drill. There obviously are other ways you can do this.

I’ve mentioned my own personal struggles keeping stats while my team is in action. I really don’t like having to take my eyes off the play to tick a box on a clipboard or tap a tablet. Working by myself, or with limited coaching help, while I was at Exeter and Svedala, I was forced to find ways to do what I wanted or needed to do in terms of training. I had to give some thought to how I can do the same thing with stat collection.

Ideas are certainly welcome!

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