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Karen Khachanov of Russia returns to Novak Djokovic of Serbia during the 2018 Mubadala World Tennis Championship in Abu Dhabi, the United Arab Emirates (UAE), on Dec. 28, 2018. Novak Djokovic won 2-0. (Xinhua/Mahmoud Khaled)
Karen Khachanov of Russia returns to Novak Djokovic of Serbia during the 2018 Mubadala World Tennis Championship in Abu Dhabi, the United Arab Emirates (UAE), on Dec. 28, 2018. Novak Djokovic won 2-0. (Xinhua/Mahmoud Khaled)