Bruin Sports Analytics
How Do Serve Errors Impact UCLA Men's vs. Women's Volleyball Performance?
By: Paige Lee and Bryan Palmero
Volleyball is a sport defined by its mistakes.
Hitting a ball into a net, sailing a serve out of bounds or failing to receive - simply put, errors are woven into the fabric of the 128-year old game. They’re terminal actions, and mark the end of rallies.
At the service line, the game of volleyball hangs in the balance. It’s where points begin, and where they can just as easily come to an end.
A common refrain among players and coaches is that serving is less of an offensive tactic than a defensive play. And with it, come some creative schemes. Strong, staunch and speedy jump serves have become the norm in their respective game. On the women’s end, shifty, tricky and aggressive float serves are preferred. But regardless of the defensive strategy, service errors are secondary to service aces - points scored when the opponent can’t receive the ball - with serving itself holding a negative expected value as a play.
The UCLA men’s and women’s volleyball teams, two of the most storied collegiate programs in the history of the sport, are no exception to the trend. Yet for two extremely successful programs, is failure at the most integral part of the game a necessary evil? And how much so?
Nowadays, we have the numbers on a team’s service aces and service errors, and with a little bit of work we can calculate sideout percentage, a statistic that measures a team’s offensive efficiency when receiving the ball to start a rally. And the numbers are not pretty.
As mentioned earlier, service errors outnumber service aces for both programs. Across six 30+match seasons, beginning as early as the 2017 calendar year, there’s no one season with a positive ace-error differential. While the women’s team kept its ratio around 1.5 errors to aces, that number doubles for the men’s side.
This shouldn’t be a surprise. Aces are hard. And when you’re trying to catch an opposing team off guard, playing cautious at the service line can leave your opponent with a ball it can easily receive, set and attack, where it will likely score the point anyway. As a result, sideout percentages for matches are usually above 50% - receiving teams win the rally more often than not.
Knowing it’s likely to lose the point anymore, a team now has more liberty to take more risks with its serving. Hence, the higher number of errors. But those are points that are lost, so how does that influence the outcome of the match?
We calculated set score margin, which for a five-set match is the margin of victory a team sees. Ranging from +3 (a clean victory in three sets) to -3 (being swept and losing), we can see that for both UCLA men’s and women’s volleyball, as the percentage of serves being errors increases, the set score margin tends to decrease. The more serve errors that are made by UCLA, the closer the overall match tends to be (in terms of sets won) between UCLA and their opponent.
In other words, losing the service battle in terms of errors leads to a higher likelihood of a loss. Hitting the ball into the net, sailing a serve out of bounds or committing a foot fault all lead to points scored for the other team, so this kind of trend should be intuitive. Still, the relationship isn’t exactly linear, though. It’s not a great fit and teams still often win with a high number of service errors - it’s why UCLA men’s volleyball and Team USA head coach John Speraw has repeatedly said on the record about his indifference with the mistakes at the line.
But what about the effect of service aces on success? Aces are uncommon compared to errors, but we can see a positive correlation with it and in-match success. For both UCLA men’s and women’s volleyball, as the percentage of aces per game increases, the set score margin tends to increase. The more aces, the greater the difference between the number of sets won between UCLA and their opponent.
Looking more closely brings us to the individual rallies played out during a set. The converse of sideout percentage is point scored percentage, which measures a team’s offensive efficiency when it is the server on a rally. As mentioned previously, teams usually have a sideout percentage larger than 50%, resulting in a point scored percentage that falls below that.
But looking at point scored percentage can give us insight on how serving can influence the outcome of a match. Not all serves will score instant points (aces), but catching the opposing team off guard with a serve can lower its opponents’ comparative advantage.
One caveat: volleyball is a rally sport which allows teams that scored the previous point to serve. A team which scores more points as the server or tallies more aces is usually the better squad, paving the way for numbers, or graphs like the one above.
For both UCLA men’s and women’s volleyball, as the percentage of points scored from serves per game increases, the set score margin tends to increase. The more points scored from serves, the greater the difference between the number of sets won between UCLA and their opponent.
Better serving tends to mean more success for teams, but it’s not the defining characteristic of a winning offense. Teams generally lose the point when they’re serving and coaches are acutely aware of that. Given the difficulty of serving, teams have more liberty to take more risks at the line.