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MELBOURNE, AUSTRALIA - JANUARY 24: Tennys Sandgren of the United States plays a backhand in his quarter-final match against Hyeon Chung of South Korea on day 10 of the 2018 Australian Open at Melbourne Park on January 24, 2018 in Melbourne, Australia. (Photo by Cameron Spencer/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  Tennys Sandgren of the United States plays a backhand in his quarter-final match against Hyeon Chung of South Korea on day 10 of the 2018 Australian Open at Melbourne Park on January 24, 2018 in Melbourne, Australia.  (Photo by Cameron Spencer/Getty Images)