ABU DHABI, UNITED ARAB EMIRATES - DECEMBER 30: Rafael Nadal of Spain reacts during day two of the Mubadala World Tennis Championship at Zayed Sport City on December 30, 2016 in Abu Dhabi, United Arab Emirates. (Photo by Francois Nel/Getty Images)
ABU DHABI, UNITED ARAB EMIRATES - DECEMBER 30: Rafael Nadal of Spain reacts during day two of the Mubadala World Tennis Championship at Zayed Sport City on December 30, 2016 in Abu Dhabi, United Arab Emirates. (Photo by Francois Nel/Getty Images)