Britain Tennis - Serbia v Great Britain - Davis Cup Quarter Final - Tasmajdan Stadium, Belgrade, Serbia - 16/7/16 Great Britain's Andy Murray Action Images via Reuters / Jason Cairnduff

A man sits on top of a rickshaw loaded with card boxes at a wholesale market in the old quarter of Delhi, India, August 2, 2016. REUTERS/Adnan Abidi

Brazilian soccer legend Pele poses for picture after receiving an Olympic necklace from President of the International Olympic Committee (IOC) Thomas Bach at the Pele Museum in Santos, Brazil June 16, 2016. REUTERS/Paulo Whitaker

2016 Rio Olympics - Copacabana - 29/07/2016. Soldier in Copacabana. REUTERS/Ivan Alvarado

A Brazilian Army Forces soldier patrols on Copacabana beach ahead of the 2016 Rio Olympic games in Rio de Janeiro, Brazil, July 18, 2016. REUTERS/Ricardo Moraes

Workers do some last minute details on the Engenhao Olympic Stadium a day before the opening soccer match of the Rio 2016 Olympic Games, in Rio de Janeiro August 2, 2016. REUTERS/Pedro Fonseca

Workers do some last minute details on the Engenhao Olympic Stadium a day before the opening soccer match of the Rio 2016 Olympic Games, in Rio de Janeiro August 2, 2016. REUTERS/Pedro Fonseca

Arthur Ashe Stadium is seen at sunset ahead of the mens final between Roger Federer of Switzerland and Novak Djokovic of Serbia at the U.S. Open Championships tennis tournament in New York, in this file photo dated September 13, 2015. REUTERS/Lucas Jackson