When Data No Longer Stands on the Coach's Side

I still remember that evening at the office, the computer screen glowing with three pages of analytical reports that not a single line of was usable. Four in the morning, I finished typing the last line of the report I would send to the newsroom, and it contained only one sentence I believed to be true: we do not have enough information to conclude anything. It was the first time in eighteen years of following professional volleyball that I was forced to admit that the emptiness of data is itself a form of data in its own right.

Over the past decade or so, the sports analytics industry has undergone a quiet but comprehensive revolution. Data centers of major leagues across Asia, from Vietnam's women's V.League to China's national championships, have all been equipped with real-time data collection systems. Every rally, every step, every coaching decision is recorded and classified. In theory, we have never had more data. But we have also never had more data being left blank, dropped, or mishandled. A failed serve in the fifth set can be logged as a technical error, but behind it lie three fewer rest days than the opponent, an unhealed ankle sprain, and pressure from the bench. Those things never appear in a statistics table. And when the statistics table is completely empty, even the best analyst can only sit still.

When I worked at a sports science research center in Beijing, there was a period when I was responsible for processing input data for matches in the national competition system. The system sometimes had transmission failures, and the entire match data would vanish from the server. What was remarkable was that those matches still took place in front of thousands of spectators. There were still scorers, still defenders, still coaches shouting from the touchline. But in the system, that match did not exist. On days like that, I would often stay long after hours, asking myself: if the data could not capture that moment, does that moment still exist. And the answer, after many years, remains yes, in a way no spreadsheet can touch.

For Vietnamese volleyball fans, this is not a distant story. Domestic leagues in recent years have seen strong investment in data analytics systems, with major clubs spending billions of dong each season on player tracking software. National team coaching staffs also rely on these metrics to select lineups, build tactics, and assess form. The problem lies in the fact that a metric only has value when placed in the right context, and context is often the first thing forgotten when data is entered into a machine. A high spike success rate can reflect the quality of the opposite hitter, but it can also simply reflect the opponent deliberately conceding a set to conserve energy. A good first-pass rate can indicate the stability of the libero, but it can also hide the fact that the opposing team hits only soft balls to limit injuries before the important qualifying round.

I think of a women's volleyball World Cup semifinal I followed in Japan a few years ago, when an Asian team led by two sets and then lost in reverse in the fifth. The post-match statistics showed the winning team had a higher attack scoring rate, better blocking rate, and fewer unforced errors. But when I reviewed the footage twice as usual, what I saw was completely different. The losing team did not lose because of technique, but because in the last two sets, their coach repeatedly delayed the timing of calling video challenges and substituting players half a beat later than the opponent. The data does not record that hesitation. The statistics table has no cell for the indecision of the person sitting in the coaching chair.

Here, I believe what is more concerning is the trend of turning data into a shield of responsibility. When a coach makes a controversial decision, the common answer is: the analysis system suggested it. When a young player is not fielded, the reason given is: training metrics have not met the requirements. Data becomes an excuse to avoid responsibility for what the naked eye can see. This is particularly dangerous in the context of Vietnamese volleyball building a new generation, where players aged eighteen to twenty-two need real match opportunities, not assessments based on fifteen minutes of training recorded on some Tuesday morning.

Of course, I am not opposed to using data. On the contrary, I believe that without data, Vietnamese sports will struggle to close the gap with Asia's leading volleyball nations. The problem is not with data, but with how we treat the gaps in data. A gap that is properly identified can be more trustworthy than ten numbers entered in haste. That is what I learned after years of working with both machines and people, and it is also why I started jotting down what my eyes saw before opening the statistics table.

In the ongoing annual season, as teams prepare to enter the sprint phase with a dense schedule, I believe fans should observe a little more carefully those plays that do not appear on the scoreboard. An opposite hitter raising a hand to call for the ball and then lowering it after five seconds of thought. A coach turning to an assistant, then not calling a timeout despite the team conceding three consecutive points. A team keeping the same lineup despite fitness clearly declining in the fourth set. Those gaps say more than any number in a post-match report. And sometimes, accurately counting a gap is more important than counting ten times over something already known.

The ball is only a supporting actor; the real drama lies in the gap between two midfield lines. The same holds in volleyball, and perhaps even more so than in football, because here every point is counted by each touch of the hand, each step of those who never appear in a standout statistics cell. The Moscow night does not belong to the scorer, but to the one who made the whole world bounce. In Vietnam, perhaps we too should begin searching for people like that, not through data tables, but through the patient eye of someone who sits long enough to see what others miss.

The question I leave open for professionals like me: if tomorrow the national men's volleyball team's data system stopped working for three weeks before a major tournament, would we still be capable of watching the ball with the naked eye.