London - World No 1 and defending champion Novak Djokovic was facing Wimbledon humiliation on Friday before rain saved him from his worst defeat at the tournament since 2008.
Three-time winner Djokovic, who is halfway to the first calendar Grand Slam in 47 years, dropped the first two sets of his third round clash against American 28th seed Sam Querrey 7-6 (8/6), 6-1.
But after just 73 minutes of action, rain sent the pair running for cover off Court One, giving 12-time major winner Djokovic welcome sanctuary before play was called off for the day.
By the end of Friday, which had seen just three hours of action on outside courts, only 15 of the scheduled 32 ties had been completed.
That led organisers to decide that for the first time since 2004, and only the third time in history, play will take place on the middle Sunday
Djokovic, who has an 8-1 record over Querrey, has made at least the quarter-finals on his last seven visits to Wimbledon since losing to Marat Safin in the second round eight years ago.
In contrast, seven-time champion Roger Federer had the advantage of playing under the Centre Court roof and became the first man in the fourth round thanks to a 6-4, 6-2, 6-2 win over Britain's Daniel Evans
Federer, beaten in the last two finals by Djokovic, has been aided by a generous draw that pitted him against two lowly Brits in world number 772 Marcus Willis and then world number 91 Evans.
"I didn't make the draw but it's been fun playing against Marcus and now Dan," said Federer who now has 305 Grand Slam singles match victories, which moves him within touching distance of Martina Navratilova's record of 306.
The All England Club, which has suffered three severely-hit rain days in the first week, said that playing on Sunday was needed to catch-up.