Ben Raymond, Adrien Ickowicz, Hugh Nguyen, Mark Lebedew.

The long-running Australian Volleyball League has been rebadged in 2023 as the Australian Volleyball Super League, with a new format and rule changes intended to make the competition more appealing to fans and broadcasters. The primary aim appears to be to achieve shorter and more predictable match durations to fit in a 90-minute broadcast window, along with loosely-articulated appeals to viewer interest including “tactical scoring plays” and “more consequences more often”.

Changes to volleyball rules are not new. The sport’s international organising body the FIVB has made many changes in efforts to improve various aspects of the sport (e.g. changing from sideout to rally point scoring in 1999 to make match durations more predictable and thus more suitable for television coverage, and introducing the defensive specialist libero position in 1998 to reduce the dominance of attacking and to extend rallies). Individual leagues have also made changes, generally motivated by marketability or similar considerations, perhaps most recently the Athletes Unlimited league in the USA and the Indian Prime Volleyball League.

What are the changes?

The rule changes for the 2023 Australian Volleyball Super League are:

These first two rules are similar to the Prime Volley League, although sets are played to 15 points there. Other smaller changes have been made to in AVSL reduce downtime (no timeouts, shorter intervals between sets, less changing of ends).

The biggest change in AVSL is the introduction of “power plays”. It’s not entirely clear what the motivation for introducing the power play was, but it seems likely that it was inspired by similar additions to sports such as limited-overs cricket and Fast5 netball. The power play is being described by the AVSL organisers as “momentum-shifting” and “can be used by a team to grab the initiative at crucial moments in a set”. It will make matches a little shorter — but this could have been achieved simply by playing sets to (say) 15 points instead of 18. The AVSL power play rules are:

Competition points are also handled differently. In standard FIVB competitions, a team is awarded 3 competition points if they win a match 3:0 or 3:1, 2 points for a 3:2 win, 1 point for a 2:3 loss, and 0 points for a 1:3 or 0:3 loss. In AVSL, teams will instead be awarded 2 competition points for every set they win (remembering that all 5 sets are played). There is also a bonus point on offer for teams that win by 20 or more points in total (added up over the 5 sets), or that lose by no more than 10 points in total (this includes the scenario where the losing team scores more points in total than the winning team).

Finals matches will be slightly different again, reverting to a best-of-5-set format and two-point margin required to win a set.

How will these affect the game?

The format has apparently been trialled with feedback from players, coaches, and broadcasters, but it is not entirely clear what the effects on the game will be.

We use the volleysim R software package to simulate matches between two teams under different rule scenarios. This package allows us to simulate theoretical set and match outcomes under different assumptions of team strength and game rules. For all simulations here we assume two closely-matched teams: team 1 has an average sideout rate of 62%, and team 2 is slightly weaker with an average sideout rate of 60%.

Bear in mind that these sideout rates are averages. When simulating a single rally, the winner is chosen at random with the probability determined by the corresponding sideout rate. Thus, over a very large number of rallies, the two teams’ sideout rates in the simulations would converge to exactly these values. But over a smaller number of rallies (e.g. one set) the random nature of the simulation means that the weaker team can win the set, even though their average sideout rate is lower.

The simulations use an idealized representation of volleyball, without real-world phenomena such as momentum, fatigue, rotational mismatches, or psychological effects that might have an impact on real games. Nevertheless, they can give us some insights into the likely effects of the rule changes.

Standard rules

Let’s first establish how our two teams would compare under standard volleyball rules (best-of-5-sets format, sets 1 to 4 played to 25 points, etc). Under these rules we expect team 1 to win 61% of matches. Using the standard FIVB competition points scheme, team 1 would be expected to obtain 46% more competition points than team 2 (if these two teams only ever played each other).

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46

Now let’s see what the effects of the new AVSL rules will be. We’ll add the new rules one at a time and evaluate the changes.

Play to 18 points

AVSL sets are all played to 18 points (normal sets are played to 25 points for sets 1-4, and 15 points for set 5). What happens when we apply this rule?

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41

Changing from 25 points (15 points in set 5) to 18 points in all sets doesn’t make much difference, so if it makes the match shorter then this seems like a reasonable rule adjustment. But it doesn’t guarantee shorter matches: we still have a requirement to win a set by at least a two point margin, so a close set could drag on for a long time if neither team can string together the consecutive points required to win the set.

One-point margin

AVSL requires only a one-point margin required to win a set (i.e. first team to 18, not first team to 18 with at least a two-point margin). This is clearly about limiting the match time by eliminating the possibility of very long sets: the highest set score possible is 18-17.

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35

Using a one-point margin is slightly beneficial to the weaker team, compared to a 2+ point margin. To illustrate why, imagine that the score is 17-17 — under a one-point margin system, the weaker team can win the set by winning just one point. Under a 2+ point margin system, a team has to win two consecutive points, which is less likely for the weaker team than simply winning one more point.

Playing all 5 sets

During round-robin matches, AVSL plays all 5 sets, rather than a best-of-5 format. Teams are awarded 2 competition points for each set won (for the moment we are ignoring the bonus competition points. We’ll add those in the next step).

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35
All 5 sets to 18 points, 1 point margin 59* 1.23

The match win percentage is included here for completeness, but marked with an asterisk because it is no longer particularly meaningful. Teams accrue points based on sets won, not matches won. The change to playing 5 mandatory sets and awarding 2 competition points per set won is clearly of benefit to the weaker team, substantially reducing their deficit in competition points.

Bonus points

A team gets a bonus competition point if they win a match by 20 or more points in total (added up over the 5 sets), or if they lose by no more than 10 points in total.

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35
All 5 sets to 18 points, 1 point margin 59* 1.23
All 5 sets to 18 points, 1 point margin, with bonus points 59* 1.21

Bonus points slightly favour the weaker team in this example (team 1 expected points ratio has dropped slightly). This is because the teams are only slightly mismatched, and the weaker team is more likely to lose by no more than 10 total points than the stronger team is to win by 20 or more total points.

Adding power plays

Simulating the addition of power plays is more complicated, because we must also assume a strategy that each team uses to call their power plays. For the purposes of this analysis, we assume that both teams use the same, very simple strategy: each team calls a power play when they reach 11 points in a set. In sets 4 and 5, they can only do so if they have a power play available (i.e. they haven’t used 3 in the match already).

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35
All 5 sets to 18 points, 1 point margin 59* 1.23
All 5 sets to 18 points, 1 point margin, with bonus points 59* 1.21
All 5 sets to 18 points, 1 point margin, with bonus points, with power plays 58* 1.18

When both teams have power plays and use them with an identical strategy, their effect appears to be minor. If anything they provide a small benefit the weaker team. This is because power plays are effectively reducing the number of rallies that a team needs to win in order to win a set. Remember that our simulation procedure, just like the real world, has some randomness. Team 2 is slightly weaker than team 1 and so will win less rallies on average, but over a finite number of rallies they might get lucky enough times to win the set. The shorter the set is, the more likely this is to happen.

Power play strategy

In reality, the two teams probably aren’t using identical strategies. How much of a difference could power plays make in theory? As an extreme test, let’s allow the weaker team to use power plays (following the same strategy as before) but the stronger team does not use power plays at all.

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35
All 5 sets to 18 points, 1 point margin 59* 1.23
All 5 sets to 18 points, 1 point margin, with bonus points 59* 1.21
All 5 sets to 18 points, 1 point margin, with bonus points, with power plays 58* 1.18
All 5 sets to 18 points, 1 point margin, with bonus points, with power plays for team 2 only 45* 0.90

We can see that power plays have the potential to have a massive impact on the game. In this case, allowing only the weaker team to use power plays reverses the advantage that the stronger team (with the 2% better sideout rate) previously had. And — although we don’t bother to demonstrate it here — advantageous use of power plays by an already-stronger team would allow them to completely dominate a set or match. While it’s unrealistic to think that one team would completely neglect to use its power plays, it’s not at all unrealistic to imagine that one team might use their power plays more effectively than the other. The result of AVSL 2023 could be decided by as much by power play strategy as by anything else.

Finals format

As noted above, the rules change again once we hit finals. Having played the round-robin matches under one set of conditions, now things are going to be different. Matches are played best-of-5 sets, to 18 points, needing a 2-point margin (with power plays). Competition points are now presumably irrelevant, it’s only match wins that will matter during finals.

Rules Team 1 match win % Team 1 expected points ratio
Standard 61 1.46
Best of 5 sets, sets to 18 points, 2 point margin 60 1.41
Best of 5 sets, sets to 18 points, 1 point margin 59 1.35
All 5 sets to 18 points, 1 point margin 59* 1.23
All 5 sets to 18 points, 1 point margin, with bonus points 59* 1.21
All 5 sets to 18 points, 1 point margin, with bonus points, with power plays 58* 1.18
All 5 sets to 18 points, 1 point margin, with bonus points, with power plays for team 2 only 45* 0.90
Finals: best of 5 sets, sets to 18 points, 2 point margin, with power plays 59

So team 1 would be expected to win 59% of finals matches, which is marginally more favourable to the stronger team than the round-robin rules were (expected match wins 58%). However, power plays will still have the potential to have a large effect on finals matches as well.

Match durations

The rule changes have certainly led to shorter and more consistent match durations. Median match play times (i.e. the time from the first serve in set 1 to the end of the last rally in set 5) from the first two rounds of the 2023 competition were 80 (max. 85) minutes for women, and 76 (max. 82) minutes for men. Compare those times to the 2022 competition which was run under standard rules: median 88 (max. 139) minutes for women, and median 83 (max. 134) minutes for men.

However, the stated aim was to fit both the men’s and women’s matches of a given fixture into a 3-hour broadcast window. The match times given above include timeouts, but not the warmup or any pre- or post-game material that a broadcast would need. The AVSL regulations call for a 10-minute on-court warmup, and both matches of a fixture are played on the same court. The broadcast might not necessarily need to show the warmup of the first match, but there has to be at least a 10 minute gap between matches to allow the second warmup, so there is an absolute upper limit of 170 minutes on the combined match time (and bear in mind that this leaves no time whatsoever for any kind of introduction or wrap-up to the broadcast, nor any unexpected delay between matches).

The round 1 SBS broadcast (Pirates vs Heat) was 3 hours and 5 minutes (185 minutes), including a combined match time (mens + womens) of 149 minutes. Round 2 (Phoenix vs Storm) was a 3:01 broadcast (181 minutes) with combined match time of 140 minutes. However, neither of these fixtures were the longest of their round. The round 1 fixture between Vipers and Steel comprised 166 minutes of match time, and round 2 Steel vs Pirates 168 minutes. Cramming fixtures of this length into a 180-minute broadcast window might be difficult.

Summary

The AVSL rule changes have led to shorter matches, but possibly not short enough to satisfy the stated broadcast requirements. The rule changes will also reduce the disparity between stronger and weaker teams, making match outcomes closer and less predictable.

The likely consequences of adding power plays to the game are difficult to assess, and different participants might ultimately view them quite differently. To spectators, the power play probably appears to be a new tool with which a team can score extra points, echoing the pre-season marketing. However, if both teams use their power plays effectively, our simulations suggest that their effects are likely to largely cancel out and have little overall effect on the game. Used poorly, on the other hand, power plays have the potential to put a team at a massive disadvantage, and so coaches might tend to view power plays as more of a liability than an asset. It would certainly seem unwise for a team not to consider its power play usage carefully. This might go so far as to distract coaching staff from other match preparation, or even compromise a match plan.

Will these changes be the catalyst that “engages the fans and creates a connection to our sport” through a “national television audience”? Or is the game format and its lack of suitability for conventional media broadcasters perhaps not the primary barrier to the growth of volleyball as a spectator sport in Australia?

You can see a leaderboard of player and team stats for the AVSL here.