There’s a post on the Off the Block blog looking at the correlation between Aces/Set and winning from the 2021 Men’s NCAA Division I/II season. I wrote previously about the correlation of various stats to league performance. The finding was that while Aces/Set does positively correlate to Match Win%, it’s well down the list. I’ve expanded the dataset since that initial analysis, but the findings remain. The correlation between Aces/Set and conference Win% is about 0.4 (positive 40%). That’s about the same as Blocks/Set and around half that of Hitting Efficiency.

I also have values for Opponent Aces/Set, which is mentioned in the article as well. Interestingly, that correlation comes in at about -0.6. And when it comes to the spread between yours and the other team’s, that registers at about 0.7. So not getting aced is even more important than getting aces.

Focusing just on the men

I should note that the values above are based on all NCAA divisions of both the men and the women. The data covers the period from 2013 to 2019. If I include just the men’s data, it cuts the sample size down by more than 90%. There’s still enough (654 observations) to work with, though.

Perhaps not surprisingly, aces are more important in the men’s game. Aces/Set has a 0.6 correlation to Match Win%, while opponent aces are at about -0.7. Thus, giving away aces is still more of a negative than getting them is a positive. The Ace/Set differential correlates at almost 0.8

Looking at percent rather than per set

There’s a certain built in bias when it comes to Aces/Set. That is better teams generally get more opportunities to serve. All else being equal, the inevitable result is more aces. For that reason, looking at Ace% (aces divided by total serves) is potentially useful.

When looking at the full dataset, a team’s Ace% only correlates at about 0.2 to Match Win%. By comparison, Opponent Ace% is nearly -0.5, while the spread between the two registers at almost 0.6. For the men’s-only subset the Ace% correlation is about 0.4. Opponent Ace% is -0.6, while the Ace% spread is at about 0.7.

By comparison, Kill% in the men’s game correlates at nearly 0.8 and Block% at 0.6.

Comments? Observations?

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John Forman
John Forman

John is currently the Talent Strategy Manager (oversees the national teams) and Indoor Performance Director for Volleyball England, as well as Global Director for Volleyball for Nation Academy. His volleyball coaching experience includes all three NCAA divisions, plus Junior College, in the US; university and club teams in the UK; professional coaching in Sweden; and both coaching and club management at the Juniors level. He's also been a visiting coach at national team, professional club, and juniors programs in several countries. Learn more on his bio page.

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