Machine Eyes and Human Eyes: Professional Tennis and the Fairness Question

On the night of August 31, 2026, at Flushing Meadows, an empty chair appeared along the sideline of Arthur Ashe Stadium. It was the chair of a line judge — a person who had stood there for more than a century, bending with every ball, raising a hand decisively when the ball touched the line. As the pandemic forced the entire sports world to retreat, the US Open organizers decided to replace the entire line-judging crew with the Hawk-Eye Live system. The word “out” no longer came from a human mouth. A synthesized voice emerged from the speakers, steady and emotionless, calling each failed shot.

I sat in front of a screen in Hai Phong, the clock nearing three in the morning Vietnam time, and realized I was witnessing something larger than a tournament. A link in tennis’s chain of justice had just been replaced. There was no argument, no loud protest. Only the silence of a profession quietly disappearing, and one thing few people noticed: when machines judge in place of humans, what do we gain, and what do we lose?

To understand why that chair vanished, we need to go back a few milestones. In 2026, Wimbledon first brought Hawk-Eye onto the grass, but at that time the technology played only an advisory role: players were entitled to challenge a shot, and the chair umpire still made the final ruling. Each set, each player had three challenges; if correct, the challenge was retained. It was an elegant mechanism that reconciled two things: the machine’s accuracy and human authority.

Then habits gradually changed. In 2026, the Grand Slams simultaneously adopted the serve clock — 25 seconds — forcing players to decide within a strict timeframe. In 2026, the US Open and Australian Open took another step: Hawk-Eye Live fully replaced line judges. In 2026, the Grand Slams allowed coaches to communicate instructions from the stands, breaking a rule that had existed for decades. Step by step, the authority to judge and the authority to decide were transferred to the system.

For Vietnamese audiences, this shift happened in silence. We watch the Grand Slams in the late-night slot, when Melbourne, Paris, London or New York are still awake. We are used to waiting a few seconds for Hawk-Eye to reconstruct the ball’s trajectory, used to the three-dimensional graphic appearing on screen, and used to trusting it more than our own eyes. A generation of viewers has grown up without ever seeing a real line judge at work at the US Open.

Something strange happens when you remove the line judge from the court: the match flows faster. No more pauses for arguments, no more sharp glances toward the sideline, no more players raising a hand to ask for a review. Technically, this is a clear improvement. But I have learned, after many years of reviewing footage, that whenever we remove a layer of people from the system, we do not only remove their errors — we also remove the very ability to see the system’s own errors. There are line calls no one sees, but the camera never blinks. And precisely because of that, the camera never knows what it has missed.

In modern tennis, data has become flesh and blood. Every player steps onto the court with a team behind them: a coach, a fitness specialist, a doctor, and increasingly, a data analyst. Before the match, they build a portrait of the opponent through metrics: first-serve success rate, points won on second serve, serve-direction tendencies when behind in the score, the average length of rallies. During the match, those metrics update continuously on the screens of the technical area.

But the rhythm of a tennis match does not live in a spreadsheet. It lives in a player’s breathing, in the way a crowd falls silent before a decisive point, in the moment a competitor chooses to gamble instead of playing safe — things no measure can capture. Data analysts are now penetrating the locker room, and their conclusions often drift apart from the real rhythm of the match. I once watched a young player paralyzed by his own data: he knew the opponent’s weaknesses so well that he forgot his own strengths. Correct analysis, placed in the wrong spot, can become a burden.

In terms of rules, three major changes over the past decade have reshaped the game. The 25-second serve clock shortened dead time, forcing players to decide faster. Hawk-Eye Live removed line judges. And allowing off-court coaching broke one of the oldest principles of this individual sport — the principle that a player must face the hardest moment alone, with no one whispering in their ear. Each change has a legitimate reason: fairer, faster, more transparent, more attractive for television. But added together, they paint a different picture. Tennis is gradually becoming a sport operated by systems, where the human element — with all its uncertainty and emotion — is pushed to the margins.

Behind the court, a vast economic machine is at work. Broadcast rights, sponsorship, prize money, fan data — all of it needs a clean, easily consumable product, without drawn-out controversies interrupting the broadcast. Technology does not appear by itself; it appears because someone pays for it. When a tournament can shorten broadcast time, increase the number of rallies per hour, and eliminate awkward disputed situations, that is a bargain for both organizers and broadcasters. What is worth reflecting on is this: are we optimizing tennis for the viewer, or for the advertising board? Those two goals often overlap, but not always. Uncertainty — the very thing that makes sport compelling — is the hardest thing to sell to a sponsor.

In the press, the story is usually told in one direction. A controversial shot becomes a sensational headline. A young player who wins a big match is canonized. A defeat is reduced to a crisis. I have written many times about shots no one mentions — situations that changed the course of a match but never made the evening news, because they had no pretty image to sell. The justice of a match often lies in those hidden corners. I find those shots at two in the morning, after everyone has gone home, when the stands go dark and only my screen is still lit.

Based on my experience following matches across many seasons, one pattern repeats: the most serious errors rarely come from a single decision, but from a lack of consistency in how the rules are applied. A shot is called one way in the first set, but another way in the last. One player is warned for a time violation, another is ignored. Such inconsistencies never appear on the scoreboard, but they erode viewers’ trust bit by bit.

And here is what I always remind myself: the biggest mistake is not blowing the whistle, but refusing to own your whistle. I once made an error in a major match, and I spent three weeks reviewing the entire tournament, noting every situation, only to understand where I had gone wrong. No one forced me to do that. But if someone in charge of officiating cannot hold themselves accountable, then no amount of good technology means anything.

Technically and tactically, removing line judges changed player behavior in ways few anticipated. Previously, a challenge was both a tool for seeking justice and a tactical card. Players used it to break the opponent’s serving rhythm, to catch their breath after a long rally, to pause the flow of the match when everything was going against them. When Hawk-Eye Live eliminated the human element entirely, that card disappeared. The match became more continuous, but also offered fewer breaks — and that changed how players allocate energy, how they build a plan for each set.

In terms of generations, tennis is undergoing a rare transition. The generation of Roger Federer, Rafael Nadal and Novak Djokovic dominated for nearly two decades, and now yields the stage to younger names such as Carlos Alcaraz or Jannik Sinner. Notably, the new generation grew up with data from their earliest days of training. They were not only taught how to hit; they were taught how to measure, how to analyze, how to optimize every serve through video and numbers. The result is a different style of play: faster, stronger, less instinctive. Is that progress? Largely, yes. But the price is the qualities that are hard to measure — sudden creativity, the ability to turn a match with a wild idea that no data table could predict.

In terms of operations and risk, the packed calendar remains an unsolved problem. Players move constantly between continents, between different surfaces, and their bodies endure enormous pressure. Technology can now track every step, every heartbeat, every sign of overload. But fitness data is only useful when placed beside the player’s own sensation. I have seen cases where an athlete was convinced by the numbers that he was fine, while his body was sending the opposite signal. Following machines too much can lead to injury; following instinct too much can lead to burnout. The balance point lies in between, and it always requires a person clear-headed enough to weigh it.

For Vietnamese tennis, the stories above may sound distant. We do not yet have a player regularly appearing in the main draw of Grand Slams, nor a youth-development system strong enough to produce world-class names. But we have something else: a patient community of fans, ready to stay up late to follow matches half a world away. And that community is learning very fast. Vietnamese viewers today no longer watch only to know who wins; they watch to understand why. They debate tactics, fitness, and refereeing decisions. That is an important foundation, because a tennis nation can only develop when its audience understands the game deeply enough.

Here I want to say something that may irritate many people: absolute accuracy can be the enemy of tennis.

Imagine a technically perfect match. No shot is called wrong. No decision is controversial. No moment makes the crowd hold its breath because it does not know where the ruling will land. It sounds ideal. But let us be honest: those very moments of uncertainty are why we sit in front of a screen at three in the morning.

When Hawk-Eye calls a ball, it does not hesitate. It does not tremble. It has never felt the fear of making a mistake in front of tens of thousands of spectators. And precisely because of that, it cannot deliver what humans deliver: a moment of courage. An umpire who dares to make a hard decision, then faces the consequences, is a story. An algorithm that makes the right call, then goes silent, is no story at all.

This does not mean I oppose technology. I oppose the naivety of believing that technology is the end point of every dispute. Machines have blind spots too: they depend on cameras, on reconstruction algorithms, on the assumption that the ball is a mathematical point moving through an ideal space. Meanwhile, a tennis ball is a deformed, spinning object that distorts when it touches the court. Nothing is perfect. A single millimeter can change the fate of an entire set, and I have learned to live with that — not by trusting the machine absolutely, but by admitting that every system, however sophisticated, is only one way of seeing, not the truth.

I do not wish for tennis to return to the era of human eyes alone. I wish for it to remember that it once had human eyes. That behind every ruling was a person who weighed, who hesitated, who took responsibility. When the line judge’s chair was dismantled, what was lost was not merely a job, but a reminder that fairness is made by people, and can also be damaged by people. An umpire is the only person on court who is not allowed to take sides — and I stand behind them. Technology will keep advancing. What remains to be answered is not whether we should use it, but whether we still remember how to take responsibility when it makes a mistake.