Attack Efficiency and the Data Void in Vietnamese Volleyball

Set three, score 24-22. Tran Thi Thanh Thuy rises at position four, the ball clips the block and sails wide. The scoreboard ticks over: one more attack point for the home side. In my notebook, that is the fifth ball in the set she has been blocked or hit out — meaning her attack efficiency in that set is negative. Same rally, two readings, two opposite conclusions. The stands applaud. I add another line to the "attempts" column.

Nine years covering volleyball in Vietnam have taught me that most of the numbers read aloud in press rooms measure nothing at all. They simply fill the gap.

Context: the league has numbers, the reporters do not

In the V-League or the national championship, detailed rally-by-rally statistics are still not the default. Organisers record points, service errors, sometimes blocks. But a genuine analysis — who takes the first pass, who runs the quick, what the team's perfect-pass rate actually is — requires someone sitting there counting every rally, or dedicated software such as Data Volley.

Most newsrooms have neither. What they have is the scoresheet. And a scoresheet only records the final touch.

On the women's national team, names like Tran Thi Thanh Thuy, Nguyen Thi Bich Tuyen and Doan Thi Lam Oanh appear in headlines almost always attached to a point total. Very few articles mention how many passes they took, what the team's perfect-pass rate was, or how many difficult balls libero Nguyen Thi Kim Lien rescued.

I once watched an automated analysis pipeline return a nine-part report — complete with headings, tables and a conclusions section — that was entirely empty. Not one fact. Someone had spent a whole session formatting a blank page. I do not believe in luck; I believe in the error margins of the people in the hot seat. And the biggest error margin in Vietnamese volleyball is this: we have the template, but not the substance.

Core: two metrics, two worlds

This is where I want to slow down.

Volleyball has two attacking metrics that media routinely confuse. Attack success rate is points divided by attempts. Attack efficiency is points minus attack errors and times blocked, divided by attempts. They sound alike. They are not.

Take a real example. An attacker scores 22 points on 50 attempts, with 10 balls hit out and 8 blocked. Success rate: 44 percent. It looks excellent, headline-worthy. True efficiency: four divided by fifty, or 8 percent. Same player, same match. One number gets her called a star; the other says she is hurting her team.

Vietnamese volleyball almost only publishes the first half of that equation.

At the same time, the concept of a "perfect pass" is used loosely. The international federation defines it one way, domestic leagues define it another, sports reporters a third. Three definitions, three numbers, one shared name. When an article cites a "62 percent perfect-pass rate", my first question is always: by whose standard?

Then there is blocking. Blocks per set depend heavily on the opponent and on how the coaching staff assembles the block. A team that blocks a lot is not automatically blocking well; it may be blocking a lot because opponents keep attacking a weak position.

And sample size. One match proves nothing. Three matches start to show a shape. A full tournament is the minimum for judging a system.

What bothers me most is the way metrics get used to pre-paint a story. Win, and every number becomes proof of character. Lose, and the same numbers become proof of weakness. Nobody checks whether the two matches involved the same opponent, or the same serving pressure.

People call me a shock merchant; I call it reading where the money flows. In volleyball, data exists wherever money flows. National teams have analytics staff. Big clubs have them. Everyone else uses scoresheets and faith.

The contrarian angle: maybe I am asking for too much

I have to argue against myself here.

There is a reasonable case: Vietnamese volleyball has no data infrastructure, so the scoresheet is the best tool available. Criticising a tool for being imperfect is pointless.

Partly true. But there is a difference between using the best available and presenting the best available as though it were the truth. An article stating "the player scored 22 points" is honest. The same article calling her "the attacking lynchpin" on the strength of those 22 points has crossed into another territory.

I may also be wrong about the pace of change. In recent years, some tournaments have started hiring professional stat crews, and domestic sports-data platforms are emerging. Perhaps in three years this argument closes itself.

I accept that possibility. But a bubble does not burst because someone pricks it; it bursts because belief runs out. If fans keep being fed half-finished metrics and keep believing, what collapses will be their trust, not some database row.

What needs to happen

A checkable prediction: next season, at least one V-League club will publish rally-by-rally statistics, at minimum for home matches. If that happens, it is a starting point. If it does not, I will write it in the notebook, next to the negative efficiency lines.

For now, one simple rule for anyone reading volleyball coverage: when you see a metric, ask three things. What is the definition. How many matches are in the sample. And who was the opponent.

If those three cannot be answered, the metric is not data yet. It is only formatting.