Tennis great Roger Federer appears to be vulnerable to only one thing at Wimbledon, the line-judging technology called Hawkeye. The system calculates the position of the ball at several points during its flight across the net, computes its trajectory, then uses this information to determine how the ball will compress and skid once it hits the grass. Now, when a player challenges a judge’s call, Hawkeye takes over, and displays a virtual re-enactment of the ball’s flight and bounce on screens around the stadium.

Federer, who defeated Rafael Nadal to win his fifth straight title at the famous grass courts, threw a mini-tantrum in the fourth set on Sunday when the technology ruled that one of Nadal’s shots, called out by the judges, had actually glanced the line. The ruling temporarily threw him off his game, as Nadal captured the set and appeared to have the necessary momentum to win the match. Though he did prevail in the end, Federer did not have kind words for the technology, declaring at one point that it was “killing me.” In an article in the Times and a detailed post on his site, Paul Hawkins, the inventor of the technology, fired back by saying that the ball was clearly in, and Wimbledon officials stood by Hawkeye, too.—Gregory Mone