Novak Djokovic

Serbian tennis player Novak Djokovic winner of the World Sportsman of the Year award kisses his trophy during the 2019 Laureus World Sports Awards.

Serbia's Novak Djokovic kisses his trophy after defeating Spain's Rafael Nadal in the men's singles final at the Australian Open tennis championships in Melbourne, Australia.

Serbia's Novak Djokovic, right, holds his trophy as he stands with Spain's Rafael Nadal after winning the men's singles final at the Australian Open tennis championships in Melbour...

Serbia's Novak Djokovic celebrates after defeating Spain's Rafael Nadal in the men's singles final at the Australian Open tennis championships in Melbourne, Australia.

Japan's Kei Nishikori, left, congratulates Serbia's Novak Djokovic as he retired injured during their quarterfinal at the Australian Open tennis championships in Melbourne, Austral...

Serbia's Novak Djokovic celebrates after defeating Russia's Daniil Medvedev in their fourth round match at the Australian Open tennis championships in Melbourne, Australia.

Serbia's Novak Djokovic falls during his second round match against France's Jo-Wilfried Tsonga at the Australian Open tennis championships in Melbourne, Australia.

Serbia's Novak Djokovic hits a forehand return to United States' Mitchell Krueger during their first round match at the Australian Open tennis championships in Melbourne, Australia...

Match umpire Simon Canavan, right, talks with Britain's Andy Murray, centre, and Serbia's Naval Djokovic ahead of their practice match at the Australian Open tennis championships i...

Serbia's Novak Djokovic celebrates after he beats Russia's Karen Khachanov in a semi final match of the Mubadala World Tennis Championship in Abu Dhabi, United Arab Emirates.

Novak Djokovic of Serbia holds his runner-up trophy after lost the ATP World Tour Finals singles final tennis match against Alexander Zverev of Germany at the O2 Arena in London.

Alexander Zverev of Germany kisses the trophy after defeating Novak Djokovic of Serbia, right, in their ATP World Tour Finals singles final tennis match at the O2 Arena in London.

Novak Djokovic, of Serbia, plays a return to Marin Cilic, of Croatia, during their ATP World Tour Finals singles tennis match at the O2 Arena in London.

Novak Djokovic of Serbia celebrates after defeating Alexander Zverev of Germany in their ATP World Tour Finals men's singles tennis match at the O2 arena in London.

Novak Djokovic of Serbia celebrates winning a point against John Isner of the United States in their ATP World Tour Finals tennis match at the O2 Arena in London.

Novak Djokovic, of Serbia, holds the trophy after defeating Juan Martin del Potro, of Argentina, during the men's final of the U.S. Open tennis tournament, in New York.

Novak Djokovic, of Serbia, celebrates after defeating Juan Martin del Potro, of Argentina, in the men's final of the U.S. Open tennis tournament, in New York.

Novak Djokovic, of Serbia, celebrates after defeating Juan Martin del Potro, of Argentina, in the men's final of the U.S. Open tennis tournament, in New York.

Novak Djokovic, of Serbia, celebrates after defeating Kei Nishikori, of Japan, during the semifinals of the U.S. Open tennis tournament.

Novak Djokovic, of Serbia, reaches for a shot from John Millman, of Australia, during the quarterfinals of the U.S. Open tennis tournament in New York.