Serbia's Novak Djokovic celebrates with the trophy after winning his match against Austria's Dominic Thiem in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Edgar Su

Serbia's Novak Djokovic poses with his winners trophy and Austria's Dominic Thiem poses with his runners up trophy during the presentation after the match in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Kai Pfaffenbach

Serbia's Novak Djokovic kisses the trophy after winning his match against Austria's Dominic Thiem in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Kai Pfaffenbach

Serbia's Novak Djokovic kisses the trophy after winning his match against Austria's Dominic Thiem in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Edgar Su

Serbia's Novak Djokovic celebrates with the trophy after winning his match against Austria's Dominic Thiem in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Hannah Mckay

Serbia's Novak Djokovic poses with fans and the trophy after winning his match against Austria's Dominic Thiem in Australian Open Men's Singles Final at Melbourne Park, Melbourne, Australia, February 2, 2020. Djokovic endured a fierce challenge to his Melbourne Park reign before overhauling Dominic Thiem 6-4 4-6 2-6 6-3 6-4 in a thriller on Sunday to clinch an eighth Australian Open crown and reclaim the world number one ranking. REUTERS/Kai Pfaffenbach