Five-time champion Serena Williams has sensationally been dumped out of the Australian Open by unseeded Russian Ekaterina Makarova in their fourth round clash at Rod Laver Arena on Monday.
World No.56 Makarova produced the match of her life to cause the biggest upset of the tournament so far in her 6-2 6-3 win over Williams.
There were no such problems for second seed Petra Kvitova, who booked a quarter-final date with Italian Sara Errani after both won their Round of 16 matches.
Normally accustomed to blowing her opponents off the court, Williams met her match with an inspired Makarova more than matching it with the powerful American from the back of the court.
Makarova hit 16 winners compared to Williams' 24, but it was the unforced error count that really told the story with the 13-time Grand Slam champion committing 37 to Makarova's 17.
Williams' normally reliable serve also deserted her as she landed just 52 percent of first serves and won just 31 percent of points on her second serve. Her nine aces were also offset by seven double faults.
After games went with serve in the opening set, Makarova landed the crucial breakthrough in the fifth game before repeating the dose in seventh and then closing out a comfortable first set.
Williams grabbed the initiative in the second set with an early break, but Makarova hit straight back and then broke the 12th seed's serve again to edge closer to the finish line.
Serving to stay in the match, Williams saved three match points, but couldn't do it a fourth time as an errant backhand gave Makarova the biggest win of her career and her first quarter-final appearance at a Grand Slam.
Makarova will play either fourth seed Maria Sharapova or 14th seed German Lisicki in the last eight.
Earlier, Kvitova continued her march towards a second Grand Slam title with a straight-sets victory over Ana Ivanovic.
Kvitova put on a clinical display as she overpowered the Serbian 21st seed in a 6-2 7-6 (7-2) win in 85 minutes at Rod Laver Arena.
The Czech star has the chance to reach No.1 in the world with victory at Melbourne Park, which would be her second major title in less than a year following her success at Wimbledon.
Kvitova's powerful ground strokes were too much for Ivanovic as she reeled off 30 winners to just 14 from her opponent.
Kvitova landed just 48 percent of first serves in the first set but still didn't offer up a single break point opportunity, while creating four for herself.
She converted two of those - in the third and seventh games - to comfortable take the first set in just 31 minutes.
Ivanovic had the chance to hit back early in the second, but Kvitova saved two break points before breaking the Serbian's serve in the fifth game to take a stranglehold on the match.
Nerves set in for Kvitova when serving for the match in the 10th game as she was broken to love with a tiebreaker needed to decide the set.
But in the tiebreaker, Ivanovic served up two double faults and committed two crucial unforced errors to virtually hand the match to her opponent.
Kvitova will play world No.48 Sara Errani in the quarter-finals after the Italian defeated an out-of-sorts Jie Zheng 6-2 6-1 in 86 minutes.
Errani may have only hit 10 winners for the match, but she benefited from a wayward Jie with the Chinese world No.38 committing an uncharacteristic 47 unforced errors.