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MELBOURNE, AUSTRALIA - JANUARY 24: CoCo Vandeweghe of the United States celebrates winning her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia. (Photo by Cameron Spencer/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  CoCo Vandeweghe of the United States celebrates winning her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia.  (Photo by Cameron Spencer/Getty Images)

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MELBOURNE, AUSTRALIA - JANUARY 24: CoCo Vandeweghe of the United States plays a backhand in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia. (Photo by Cameron Spencer/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  CoCo Vandeweghe of the United States plays a backhand in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia.  (Photo by Cameron Spencer/Getty Images)

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MELBOURNE, AUSTRALIA - JANUARY 24: CoCo Vandeweghe of the United States serves in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia. (Photo by Quinn Rooney/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  CoCo Vandeweghe of the United States serves in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia.  (Photo by Quinn Rooney/Getty Images)

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MELBOURNE, AUSTRALIA - JANUARY 24: CoCo Vandeweghe of the United States plays a backhand in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia. (Photo by Clive Brunskill/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  CoCo Vandeweghe of the United States plays a backhand in her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia.  (Photo by Clive Brunskill/Getty Images)

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MELBOURNE, AUSTRALIA - JANUARY 24: CoCo Vandeweghe of the United States celebrates winning her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia. (Photo by Cameron Spencer/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  CoCo Vandeweghe of the United States celebrates winning her quarterfinal match against Garbine Muguruza of Spain on day nine of the 2017 Australian Open at Melbourne Park on January 24, 2017 in Melbourne, Australia.  (Photo by Cameron Spencer/Getty Images)