Five-time champion Serena Williams crashed to one of her worst ever grand slam defeats and Japan's Kei Nishikori stunned Jo-Wilfried Tsonga on a day of major shocks at the Australian Open on Monday.
As Andy Murray reached the quarter-finals with minimal fuss, little-known Russian Ekaterina Makarova handed out one of the Open's great upsets when the world number 56 beat out-of-sorts Williams 6-2, 6-3.
Williams, who has been struggling with an ankle injury and admitted she "wasn't 100 percent", was broken five times and sent down nine double-faults to end her 17-match winning streak in Melbourne, stretching back to 2009.
The 2003, 2005, 2007, 2009 and 2010 winner, who missed last year's event with injury, has not suffered a similar grand slam defeat since 2005, when she lost to 85th-ranked Jill Craybas at Wimbledon.
But Makarova, 23, who earlier ousted Russian former world number two Vera Zvonareva, is now into her first grand slam quarter-final.
"It's an amazing feeling, it's unbelievable," Makarova said. "She's an unbelievable player and I'm just really happy."
China's Zheng Jie was also beaten 6-2, 6-1 by Italy's Sara Errani to end the country's singles interest on Chinese new year's day -- and a day after Li Na's tearful defeat to Kim Clijsters.
Williams's exit blows a giant hole in the women's draw with Wimbledon winner Petra Kvitova and Maria Sharapova, the 2008 champion in Melbourne, among the potential beneficiaries on her side of the draw.
Defending champion Clijsters was also hit by an ankle injury during her win over Li which could hinder her progress.
Meanwhile Nishikori, 22, became the first Japanese man into the Australian Open quarter-finals in 80 years as he came from a set down to shock former finalist Tsonga 2-6, 6-2, 6-1, 3-6, 6-3.
But Murray took the easy route to the last eight when Kazakhstan's Mikhail Kukushkin retired injured.
Under blazing sun Murray, seeking Britain's first men's grand slam title since before World War II, was always in command and he led 6-1, 6-1, 1-0 when Kukushkin pulled out with a hip muscle injury on 49 minutes.
The truncated match ended an entertaining run by Kukushkin, inevitably dubbed "Borat" by the British press, who won an oddball encounter in the previous round to become Kazakhstan's best male grand slam performer.
"It's so hot on the court," said Murray, who will play Nishikori in the quarter-finals.
"It's obviously good for me that I got to conserve a bit of energy. It's tough for him -- it's his first fourth round in a slam, and he's obviously struggling."
Murray remains on course for a semi-final with defending champion Novak Djokovic, who plays Australian veteran Lleyton Hewitt later, while Rafael Nadal and Roger Federer are into the last eight in the draw's other half.
In the women's competition, Kvitova reached the quarter-finals with a 6-2, 7-6 (7/2) win over Ana Ivanovic -- but not before a temporary meltdown in which she embarrassingly swung and missed a simple overhead.
The cringe-making mistake late in the second set precipitated a brief nosedive and a flurry of errors but tough Kvitova steadied herself to seize control of the all-important tiebreak.
"It was quite a hard match at the end of the second set," she said, adding that she was happy to be off the court early on a typically hot Melbourne day.
"I think I was quite lucky I played my match at 11 o'clock. It's hot, but we are in Australia so we are ready for it."
Kvitova will play Errani in the next round, while Williams's conqueror Makarova will take on either Sharapova or Germany's Sabine Lisicki.
Murray's opponent Kukushkin had caused bemusement in his five-set win over Gael Monfils, who was severely restricted by a back injury.
But the Kazakh was unable to press his advantage, resulting in a series of puzzling rallies played at half-pace.