Djokovic at his best to beat Isner in ATP finals

 Cristiano Ronaldo (C) grasps a tennis ball while sitting courtside during the single's match between John Isner of the United States and Novak Djokovic of Serbia during Day Two of the 2018 ATP World Tour Finals at the O2 Arena in London, Britain on Nov. 12, 2018. (Xinhua/Han Yan)