Angelique Kerber could not defend her Australian Open title, falling in straight sets in the fourth round. Germany's Mischa Zverev has also knocked Andy Murray, the men's world number one, out of the tournament.
The women's top seed was handed an early exit from the Australian Open on Sunday, unable to make the quarterfinals after winning the grand slam tournament last year.
In a match that lasted just 1 hour and 8 minutes, Coco Vandeweghe shocked the women's world number one in straight sets 6-2 6-3 in the Rod Laver Arena in Melbourne, Australia. The 25-year-old American, who lost in the first round of the Australian Open last year, will make her second quarterfinal appearance in a Grand Slam tournament.
"Last year I came here and didn't even win a match and here I am now," Vandeweghe added.
Kerber, who was the top seed at a major tournament for the first time in her career, had struggled in the first two rounds of the tournament, battling past Lesia Tsurenko and Carina Witthoeft in three-set matches. She seemed to have found her groove Kristyna Pliskova in the third round, but struggled to keep up with the hard-hitting Vandeweghe on Sunday.
Vandeweghe will face Spanish seventh seed Garbine Muguruza in the last eight.
Andy Murray also sent packing
Britain's Andy Murray was the first world number one eliminated from the Australian Open on Sunday. Germany's Mischa Zverev beat Murray 7-5 5-7 6-2 6-4 to remove the top seed from the tournament in an exciting match in the Rod Laver Arena.
With reigning champion Novak Dokovic also out of the tournament after his defeat to Denis Istomin on Thursday, neither the No. 1 nor the No. 2 seed will now be playing in the quarterfinals of the Australian Open, the first time this has happened since 2002.
The match between Zverev and Murray went for 3 hours and 34 minutes. Murray dropped his serve eight times.
The 29-year-old Zverev will go on to play Roger Federer in the quarterfinal after Federer beat Kei Nishikori.
The resilient 35-year-old Federer overhauled fifth seed Nishikori 6-7(4) 6-4 6-1 4-6 6-3 to secure his spot in the quarterfinal.
Sunday's defeat puts an end to this year's bid by Murray to finally lift the Australian trophy after losing five finals at the tournament.
US Open champion Stan Wawrinka of Switzerland has also advanced to the quarterfinals after his 7-6 (2), 7-6 (4), 7-6 (4) victory over Italian Andreas Seppi on Margaret Court Arena. Wawrinka, the 2014 Australian titlist, will face veteram Jo-Wilfried Tsonga of France, who beat Briton Dan Evans in four sets at the Hisense Arena.
tj,dv/rc (Reuters, dpa)