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Illinois Volleyball

What Is Point Differential And Why Does It Matter? - Part 2

Stats LessonsJoseph Trinsey

In our earlier post on Point Differential, we talked about different ways of expressing the score:

  • Total number of points (ex: 104 to 103)

  • Point Differential (ex: 50.2% to 49.8%)

  • Sideout Differential (ex: 56% to 52%)

While each of these has value, Sideout Differential probably tells us the most information, because, in addition to telling us the margin of victory (or defeat), it tells us a little bit about how that victory (or defeat) occurred. A 70% to 68% Sideout Differential tells us something different than a 50% to 48% Sideout Differential. But what else can Sideout (or Point) Differential tell us?

In terms of Sideout/Point Differential, there’s 6 scenarios that can happen:

  1. We have a large positive differential and win the match.

  2. We have a large negative differential and lose the match.

  3. We have a small positive differential and win the match.

  4. We have a small positive differential and lose the match.

  5. We have a small negative differential and win the match.

  6. We have a small negative differential and lose the match.

(There’s also the scenarios where the differential is zero and we either win or lose, but those are similar enough to scenarios 3 through 6 to lump them in together.)

Scenarios 1 and 2 aren’t too interesting. Well… maybe interesting in some ways, but in terms of statistical analysis, not so much. You were either much better or much worse than your opponent that day and there was a gap in fundamental skills. Small tactical adjustments aren’t going to erase a 7-point lead.

Scenarios 3 through 6 on the other hand, are a lot more interesting to us from a statistical perspective, and these scenarios are ones where little things can tip the balance of the match one way or the other.

These four scenarios recently played out in the NCAA Women’s Volleyball Final 4. Let’s take a look, using our handy GMS Stats app to produce the analysis.

In our post breaking down the Final Four match between Illinois and Nebraska, we saw scenarios 4 and 5 play out, depending on which side you were rooting for.

Illinois Point Differential Screen, GMS Stats app

Illinois Point Differential Screen, GMS Stats app

Illinois outscored Nebraska, but lost the match. Or, if you’re a Nebraska fan, Nebraska got outscored, but won the match. This is uncommon, but it does happen. In a 5-set match, the team that scores more points only wins about 78% of the time.(*) On the flip side, we have the Stanford - Nebraska Championship Match:

Stanford Point Differential Screen, GMS Stats app

Stanford Point Differential Screen, GMS Stats app

On average, the margin of victory in a 5-set match is about 5 points, so these two matches were close even by 5-set standards.

In the post on that match, we looked at some of the rotational matchups and how they played out. A lot of times, these matchups can be the difference in a close match. Rotational order, matchups, and clutch play are the three things I like to look at in close margins of victory.

The danger with looking at one match is that there’s a lot of randomness involved. Is that rotation in which you gave up a late-game run really a bad rotation, or did you just catch a hot server at the wrong time? This is why we like to take a multi-match view of things. In the GMS Stats app, we built that into the Wizard feature:

Point Differential Wizard Screen, GMS Stats app

Point Differential Wizard Screen, GMS Stats app

This is the Wizard screen I pulled from a 5-match sample. I was coaching a professional team and wanted to see how our performance translated into wins and losses. For a single match, this translation is simple: if you outscore your opponent, you expect to win the match. If you get outscored, you expect to lose.

But things get trickier over multiple matches. If your Differential is 2% over a half-season, what do you expect your record to be? How about 5% or 10%? Fortunately, the Wizard feature does these calculations for us!

In this 5-match sample, we had a small but meaningful 2% edge over our opponents and that resulted in a 3-2 match record. Intuitively, we probably sense that this is about right. Maybe, we figure, we might be able to go 4-1, but 5-0 feels like a stretch. On the flip side, since we’ve outscored our opponents, we probably feel like 2-3 would be a letdown and 1-4 would indicate that something is really wrong.

Over time, this Point Differential-to-record translation can give us coaching insight. We can now imagine the previously mentioned scenarios reducing down to:

  1. We are outscoring our record.

  2. We are underscoring our record.

If we were 5-0 with a differential of only 2%, this would tell us some things as coaches. The first thing it would tell us: don’t get too cocky just yet, we’re probably getting lucky! It would also indicate that, while the results are good now, we should still be looking to make some changes if we want to keep the winning streak alive. There’s always the temptation to not make changes when the team is winning, but in this scenario, changes might still be warranted.

If we were 2-3 or 1-4 with a positive point differential, it tells us something different. First of all, it tells us that we’re not doing quite as bad as we think! So, while some changes are probably necessary, they might not need to be as drastic as the record might indicate. It also tells us that we’re probably losing some close games, and we have an opportunity to close them out better.

In this case, we look at our three Close Game Factors:

  1. Rotation Order

  2. Matchups and Scouting

  3. Clutch Play

More on these factors in our next post!

(*) 5-set win % and margin of victory data provided by Volleytalk legend The Bofa on the Sofa.

NCAA Women’s National Championship Semifinal Match Analysis

Match AnalysisJoe TrinseyComment

Nebraska vs Illinois… could it be any closer?

Today we’re going to dive deeper into one of the best matches of this year’s NCAA tournament: the Semifinal between Nebraska and Illinois. The teams met twice during the regular season, and each came away with a 3-1 victory (oddly, Nebraska won at Illinois and Illinois won at Nebraska) and the third matchup between them would determine who would advance to the National Championship. With so much on the line, fans expecting a close match would not be a disappointed!

We’ll be using the new GMS Stats app (available now in the iOS App Store!) to break down these matches. Right away, you can see how close the match was:

End of match screen. GMS Stats app.

End of match screen. GMS Stats app.

Not only was the margin of difference only 1 point between the two teams, Nebraska was actually outscored by Illinois, yet still won the match! As coaches, we love when this works out in our favor, but it’s heartbreaking for Illinois.

Illinois point differential screen. GMS Stats app.

Illinois point differential screen. GMS Stats app.

Illinois outscored Nebraska by 1 point, but the margin was actually a bit greater than that in Sideout % terms. Illinois was a full 1% better than Nebraska over 207 serves, because (due to coin flips and how the end of the games worked out), Nebraska actually had 105 chances to side out, while Illinois only had 102. At Gold Medal Squared we talk about how there are, “no little things,” because we can see how razor-thin the margins are.

When matches are very close, one of the things to look at is end-of-game play. What’s interesting about the end of games is that they mirror the beginnings. The reason the starting rotation is so important is not because points scored at the end of the game matter more than points scored in the middle, or that it’s important to get off to a, “good start.” They don’t, and it’s not- at least not any more than it is important to be good every other time of the game. No, the reason the starting rotation is so important is that teams will usually rotate around two full times, serving and receiving in each rotation twice. However, the first rotation will almost always get a third turn. (In a game where both teams are siding out a lot, the teams will rotate around faster and in a game where both teams are going on long runs, they will rotate slower.)

This third turn is critical because it means that the rotational matchup you start the game with will come up at the end of the game, where you either have the chance to win the game with a run, or lose it by giving one up.

In game 2, Illinois had the serve to start and they opted to start, as they usually do, with their setter, Jordyn Poulter, as the first server. Nebraska matched up against this by receiving with their setter in 1. This can be a tough rotation for many teams, because the outside attacker is on the right side of the court, and the opposite is on the left side. In this case, Nebraska had their outside, Lexi Sun, passing in the middle of the court and attempting to hit in the middle.

Poulter attacked the seam between Sun and libero Kenzie Maloney and gave Nebraska all sorts of trouble. The first serve was an ace between Sun and Maloney. Maloney passed the second serve well, but Illinois blocked Sun in the middle. The third serve was another ace between Sun and Maloney. On the next play, Nebraska then tried to pull Sun over to the left side and stack their attackers over on that side. They got a good pass, but Sun hit out. At this point, Illinois was up 4-0. On the next play, Illinois won a rally after picking up Sun’s tip and then digging a big swing by Nebraska opposite Capri Davis and scoring in transition. Nebraska shuffled Sun back to the middle of the serve receive and Poulter served another ace into some confusion on the Nebraska side. Finally, Nebraska shifted Sun over to the right side and had Maloney and Mikaela Foecke pass in a 2-person sideout, and they got the sideout.

By then, the damage was done, and Illinois cruised to a win in the second set.

After Nebraska won the third set, Illinois would start the fourth set with the serve. Since Illinois almost always elects to start with Poulter as their first server when they serve first, Nebraska could decide whether they wanted to change their rotation to create new matchups or stick with the matchup they had in game 2, and try to execute better.

As coaches, we face this dilemma all the time! Nebraska obviously planned to receive in rotation 1 because it’s a strong rotation for them. They aren’t dumb; they have the statistics about how their rotations have performed previously. Yet as coaches, we see the matches evolve in front of our eyes and we have to decide, “do we stick with what has worked in the past, or am I seeing something that needs to be adapted to in the present?”

Nebraska opted to make a change; they backed up one rotation, so that instead of Poulter serving at rotation 1, she served at Nebraska’s “Setter-2” rotation, with Nebraska setter in zone 2, and Lexi Sun and middle Callie Schwarzenbach in the front row. This was a bold move by Nebraska, because this had not been their strongest rotation; in fact, for the match as a whole, it ended up being their weakest sideout rotation!

Nebraska rotation screen. GMS Stats app.

Nebraska rotation screen. GMS Stats app.

But in game 4, it worked out just fine. With the change in rotation, Nebraska had an additional defensive specialist in the game, as well as Maloney and Foecke, two strong passers. Sun was also freed up to be out of serve receive and on the left side of the court, to do what she does best: hammer on the left side of the court. Nebraska passed the first serve well, Sun got a good swing and Illinois was only able to bring back a freeball, which Schwarzenbach killed on the slide. For bonus points, notice how Schwarzenbach stayed in front of the setter on the first ball (possibly because the pass came off the net a little), but then went on a wide slide on the freeball. Illinois OH Beth Prince was pulled in a little tight, possibly expecting Schwarzenbach to run a quick in front or worried about Foecke attacking out of the backrow. This subtle change helped get Schwarzenbach an open net and an easy kill.

Game 4 was off to a better start for Nebraska than game 2, but they still needed to close it out. At 21-19, both teams had rotated all the way around twice and now entered the critical “third turn” that is created by the rotation order. Poulter went back to serve and Nebraska was again in their Setter-2 rotation. Nebraska was unable to sideout on the first ball. They tried Schwarzenbach on the slide, but the Illinois block was ready for her this time and slowed her down enough for an easy dig, which Illinois turned into a kill out of the middle to cut the lead to 21-20. Poulter missed the next serve and Nebraska setter Nicklin Hames ran 3 points in a row to close out game 4 and send it to a 5th and deciding set.

5th sets present some new challenges for coaches. First, the dynamics of rotations are different. Instead of rotation all the way around twice and having 1 or 2 rotations come up for a third turn, you will generally rotate all the way around once and have 1 or 2 rotations NOT come up for a second turn. So, it may be less about maximizing a good rotation and more about minimizing a bad rotation. Additionally, many coaches like to start with the rotation that puts their best attacker in zone 4, wanting to maximize the number of sets they can get her in the critical 5th game. And some coaches like to stick with what they’ve been doing and start game 5 in the rotations that have been strongest all year or in that match.

Chris Tamas of Illinois had an option that could do two of these things at once. He opted to start with the Setter-6 rotation, which put his All-American OH Jacqueline Quade in zone 4 and was also a very strong rotation overall.

Illinois rotation screen. GMS Stats app.

Illinois rotation screen. GMS Stats app.

Nebraska, possibly expecting Illinois to start with Poulter serving and wanting the same matchup as game 4, started receiving with their setter in 2. The change by Illinois created matchups that had not played out earlier in the game, which causes both teams to adjust on the fly. And because a 15-point 5th-set doesn’t create the same “third turn” as 25-point games do, this meant there was less predictability in how the end of the game would play out.

Both teams traded points throughout the whole set. At 11-11, Illinois was back to serve with their Setter-4 rotation, which was good news for them. Throughout the match, they had been strong defensively in this rotation. With defensive specialist Taylor Kuper serving, they held Nebraska to under 50% sideout. Illinois fans could reasonably expect to score at least one point and gain a critical lead late in the game.

Unfortunately for Illinois, it was not to be. Nebraska was receiving in their Setter-6 rotation, and you can see in Nebraska’s rotation screen that this was a very strong rotation for them as well. National Semifinal matchup, coming down two of each team’s strongest rotations. It doesn’t get any better!

Nebraska sided out on their first chance on a big swing by opposite Jazz Sweet to go up 12-11. On the next rally, Nebraska dug a big swing by Quade, but Foecke appeared to hit out in transition. On replay, the smallest of touches was shown, reversing the call and giving Nebraska the point. So close! Kenzie Maloney served an ace for Nebraska to put them up 14-11, and on the final point, after some fantastic defense by both teams, Foecke found the Illinois end line to give Nebraska the match and send them to the National Championship.

What a match!

There’s lots of lessons coaches can take away from a high-level match like this. For me, the biggest lesson is:

Know your strongest rotations, but be prepared to adapt to what you see. Setter-2 rotation was not especially strong statistically for Nebraska, but coach John Cook saw a passing rotation that could handle Poulter’s serve better and give them a better shot to handle the matchup that the game presented as it played out. And sometimes the margins are thinner than you can imagine, two great teams playing dead even, with a fraction of a touch on replay making the difference.

I hope you enjoyed this analysis. If you want to do your own rotation analysis, check out the GMS Stats app on the iOS App Store!