The ball streaks through the air toward the base line, topspin yanking it down right near the line. “Out,” shouts the line judge.
For 15 years, a player who disagreed could protest with a challenge, and fans at the Rolex Paris Masters, and every other major tournament, would then look to the video screens, often clapping rhythmically, building toward when the Hawk-Eye line-calling system would provide true justice.
The pandemic has changed the game. For safety, the hardcourt Masters 1000 tournaments this year, as well as the Australian and United States Opens, replaced line judges (backed up by Hawk-Eye for challenges) with a fully automated system, Hawk-Eye Live.
This system, which the ATP debuted in 2017 at its Next Gen Finals, makes instantaneous calls. Automated line calling has increased confidence in accuracy, while raising questions about the game’s human element.
A tour ruled by machines is still far in the future, but this temporary fix provides a sense of where line-calling may be headed.
To retain some human element with Hawk-Eye Live, tournaments use recorded voices instead of beeps and boops. “It would feel wrong for tennis to become too robotic,” said Ross Hutchins, ATP’s chief tour officer. (One Hawk-Eye executive publicly floated the idea of using sponsor names, so instead of “Out” you might hear “Ralph Lauren.”)
The challenge system demonstrated that line judges were right more often than players, but the machines are more accurate still. “Being the most accurate is the most important thing,” Hutchins said. Eliminating challenges also speeds up the game.
Novak Djokovic, the top-ranked men’s player, said he liked the system.
“I don’t see a reason why we need the line umpires if we have the technology,” Djokovic told ESPN this year. “I support technology. It’s inevitable for the future of tennis.”
Removing people provides more space behind the baseline for players, said Pam Shriver, an ESPN analyst and a former professional player, while automated reliability produces fewer distractions for players and thus better tennis: “It gives the players one less thing to worry about.”
But Hawk-Eye Live does not actually mark the spot — it uses its cameras and data to project an estimation of where the ball will bounce. Shriver finds the idea of projected estimates disconcerting, given potential distortions like wind gusts. “It sounds like guessing,” she said. “People think what was caught was the physical bounce as it was happening.”
Representatives from Hawk-Eye claim accuracy within 3.6 millimeters and self-reported 14 mistakes in 225,000 calls at the U.S. Open in 2020.
A rival company, Foxtenn, uses cameras to capture the ball’s actual movement.
“Our accuracy is perfect, and one thing that makes us credible is that the player sees the real ball bouncing in the replay, not a drawing,” said Félix Mantilla, director of sales and a former player. “I think only one technology will survive in 10 years.”
For now, Hawk-Eye remains the dominant player.
“We’re continuously innovating our technologies, while delivering the highest accuracy possible,” the company said in a statement.
The tour has confidence in both systems, Hutchins said, adding that there was “absolutely” room for two. Yet it took Covid — and the need to limit the number of people on the courts — to push toward live line calling. And plans are to have Hawk-Eye Live as an option on the ATP Tour through only the first quarter of 2022.
“This is not close to permanent,” Hutchins said. “We still want to understand the system’s impact more.”
Feedback from fans has been mixed, and there are issues about the impact of developing future chair umpires. Hutchins said the cost of Hawk-Eye Live would be difficult for the hundreds of junior, future and challenger tournaments to pay for, meaning line judges will remain. “There will still be a pathway for chair umpires for a very long time.”
Mantilla said that while Americans loved advanced technology and embraced these changes, Europeans were more traditional. “I don’t know if it will take 10 or 20 years for there to be no lines people left in major tournaments, but it will take time.”