How Instant Replays Changed Professional Tennis


Hawk Eye technology—and the challenge system that comes with it—has transformed the world's politest game.


It was nearing 1 a.m. New York time on Sept. 7, 2001, when the first tremors of a substantial tennis meltdown shook the U.S. Open. Fiery American newcomer Andy Roddick and his 20-year-old Aussie rival Lleyton Hewitt were in the fifth set of their quarterfinal matchup, and the pair had been trading groundstroke after punishing, sweaty groundstroke for more than three and a half hours. But suddenly, when Roddick was serving at 4-5, fate and optical illusion teamed up to do a mean, baffling thing to the teenage home-country hero.

A powerful cross-court forehand by Roddick just kissed the alley line furthest from the chair umpire, a neat trick that would move Roddick one point closer to the semifinal. Or, at least, that's what the linesman (and Andy Roddick) thought. Chair umpire Jorge Dias, from atop his perch on the other side of the court, saw something different. He overruled the line judge's call and awarded the point to Hewitt, sending Roddick into a tailspin of white-hot rage.

Afterward, TV replays would show that the ball might have actually landed in. But five points later, a still-bewildered Roddick congratulated Hewitt on his victory and then trudged bitterly out of Arthur Ashe stadium.

Fast-forward 11 years to the last match of Roddick's career—a fourth-round U.S. Open match against Juan Martin del Potro, just this Wednesday night. Early in the fourth set,Del Potro unleashed a monstrous first serve at 40-15. A line judge shouted that the serve was wide. Chair umpire Carlos Bernardes overruled, calling the serve an ace. Roddick disagreed.

But instead of scoffing, or scowling, or hurling a racket, the American simply raised his right hand. "Mr. Roddick is challenging the call," said the loudspeaker. Both panting players turned toward the stadium's JumboTron to watch a neon yellow orb travel across the screen, finishing its journey just wide of a thick white stripe. The word "OUT" appeared. Roddick was right: The serve had been long.

Then both players jogged back to the baseline. Del Potro tossed up a second serve, and play went on.

Roddick, to be sure, was an older and a wiser man when he left tennis than when he arrived (though he remained a magnificently hot-tempered one throughout his career). But it's not just Roddick who's matured since that sour night in 2001. The game has evolved, too.

Hawk-Eye instant-review technology and its accompanying challenge system made their Grand Slam debut at the 2006 U.S. Open. Since then, the provision of three challenge attempts per set has largely been appreciated as a nifty little rule tweakage that boosts convenience and helps avert would-be tantrums like Andy Roddick's. But if we look a little closer, the truth is that challenges have subtly transformed the game of tennis as we know it.

In a post-Hawk-Eye world, elite-level tennis is injected with the purest form of justice: the kind that's unblemished by human error. Six years into the regulated, widespread use of Hawk-Eye, three in every 10 challenged calls in professional tennis are overturned on the spot. Three times out of 10, in other words, machinery baldly exposes the unintentional unfairness of tennis' long-standing tradition of human umpiring. Hawk-Eye's high-precision technology has restructured the power dynamic of a sport once governed only by physics and the honor system—for better or for worse.


Hawk-Eye is the patented name for a complex instant-replay system that detects the trajectory of a tennis ball as it bounces off the court. Developed in Romsey, England, in the early 2000s, the system tracks a tennis ball's path by compiling images provided by 10 high-speed video cameras mounted strategically at different viewpoints around the court, and then compiles an image to present to players, umpires, spectators, and TV audiences just moments later—usually via JumboTron.

Hawk-Eye's instant review was first used in tennis in 2002 as part of the BBC's Davis Cup coverage, and won an Emmy the next year for Outstanding Innovative Technical Achievement. The on-court replay system got its real big break, though, in 2004. A series of controversial line judgments were proven to have worked against Serena Williams in her three-set loss to Jennifer Capriati in the quarterfinals of the U.S. Open, and a clamor arose for better, more reliable line officiating.

Hawk-Eye then began cropping up at professional-level tennis events all over the globe for instant-review purposes. Early on, tournaments were allowed to decide for themselves how many challenges players were allowed. Some tournaments gave players an unlimited number of challenges, others permitted two or three per set, and others devised systems with allotments dependent on whether the challenges had been successful.

When the news broke in the spring of 2006 that the U.S. Open would be adopting the player-challenge system that fall, players' reactions were mostly positive. James Blake, the promising onetime Harvard man positioned at No. 21 in the ATP rankings, told USA Today: "The ball's moving so fast these days that sometimes it's impossible for anyone to see, even a trained official." Roddick, Blake's compatriot, had set a new record for the fastest serve in tennis just two years before—at the dizzying, blink-and-you'll-miss-it speed of 155 mph. "With instant replay," Blake said, "we can take advantage of technology and eliminate human error."

Larry Scott, the chairman of the Women's Tennis Association at the time, also endorsed the integration of the instant review technology. "With all that's on the line in tennis these days, we felt we had to pursue every means possible to utilize technology to make sure that calls were accurate without losing the human element of officials on the court," he told ESPN. "While tennis is at a very high level of officiating, there's no denying that through this technology players and fans can know that the right call was given."

Not everybody loved the idea, of course. Roger Federer believed the money being spent on correcting "just a few points"—roughly $50,000 per court at the time—could have been better used elsewhere. "I am against the whole idea of replays," the Swiss phenom, then 24, declared. True to his word, Federer would maintain a complicated, begrudging relationship with line-officiating technology for years afterward.

But whether Federer and his fellow agnostics liked it or not, Hawk-Eye and its challenge system were here to stay. In 2008, the four governing bodies of professional tennis (the International Tennis Federation, the WTA, the Association of Tennis Professionals, and the Grand Slam Committee) bestowed their blessing on a unified set of challenge rules to be used across tournaments at the pro level: Players would be allowed three unsuccessful challenges per set, with one extra allotted if the set reached a tie-break.

Today, a hefty portion of significant matches take place on courts equipped with Hawk-Eye's high-precision line judging. Hawk-Eye is used on the show courts at three of the four Grand Slam tournaments—the lone exception being the French Open, where the dusty red clay surface itself shows the exact location of the ball's impact. Thus, nearly every high-profile early-round match, and virtually all matches after the quarterfinal stage of a major, take place on a court equipped with Hawk-Eye systems. Hawk-Eye graced the courts at the Olympics in 2008 and 2012, and it's also in use at a majority of smaller tennis venues: The Indian Wells Tennis Garden, the California home of the BNP Paribas Open, has Hawk-Eye cameras installed on every one of its eight courts—and has been said to be setting a new standard.

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Ashley Fetters is a former associate editor at The Atlantic.

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