Serena Williams was forced to pull out of her doubles match with sister Venus at Wimbledon after she became unwell on court.
In scenes which were often uncomfortable to watch, the American appeared dizzy on court and was unable to hit or bounce the ball.
After she served four consecutive double faults, umpire Kader Nouni came down to speak to the sisters as the worrying situation continued.
The sisters eventually forfeited the match against German Kristina Barrois and Swiss Stefanie Voegele after going 3-0 down in the first set.
The commentator said Williams, who has won five Wimbledon singles titles, was a "shadow of herself" and appeared to be "sleepwalking" through the match.