Djokovic at his best to beat Isner in ATP finals

Novak Djokovic of Serbia competes during the men's singles match between John Isner of the United State and Novak Djokovic of Serbia during the 2018 ATP World Tour Finals at the O2 Arena in London, Britain on Nov. 12, 2018. Djokovic won 2-0. (Xinhua/Han Yan)