Serbia's Novak Djokovic celebrates after his match against Switzerland's Roger Federer in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. Novak Djokovic once again beat great rival Roger Federer at a Grand Slam on Thursday with a 7-6(1) 6-4 6-3 win to reach the Australian Open final. REUTERS/Kai Pfaffenbach

Serbia's Novak Djokovic in action during his match against Switzerland's Roger Federer in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. REUTERS/Kai Pfaffenbach

Switzerland's Roger Federer in action during his match against Serbia's Novak Djokovic in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. REUTERS/Kim Hong-Ji

Serbia's Novak Djokovic in action during his match against Switzerland's Roger Federer in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. REUTERS/Kim Hong-Ji

Serbia's Novak Djokovic celebrates after his match against Switzerland's Roger Federer in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. REUTERS/Edgar Su

Serbia's Novak Djokovic and Switzerland's Roger Federer hug each other after their match in Australian Open Semi Final at Melbourne Park, Melbourne, Australia - January 30, 2020. REUTERS/Issei Kato