MELBOURNE, AUSTRALIA - JANUARY 21: Alexander Zverev of Germany reacts in his third round match against Rafael Nadal of Spain on day six of the 2017 Australian Open at Melbourne Park on January 21, 2017 in Melbourne, Australia. (Photo by Cameron Spencer/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 21:  Alexander Zverev of Germany reacts in his third round match against Rafael Nadal of Spain on day six of the 2017 Australian Open at Melbourne Park on January 21, 2017 in Melbourne, Australia.  (Photo by Cameron Spencer/Getty Images)