Djokovic had been favourite to win a 10th title at Melbourne Park and claim a 21st Grand Slam crown but the Serb now faces being deported from Australia.
Roger Federer clinched a record-extending 10th Swiss Indoors championship title in his hometown of Basel with a crushing 6-2, 6-2 victory over Australia's Alex de Minaur on Sunday.
Sweden's Elias Ymer replaced Berrettini in the men's draw, organisers said.
Djokovic missed the Australian Open after being deported for not having been vaccinated against COVID-19 and will not be allowed to compete at the US Open
Their epic rivalry includes three successive Wimbledon finals from 2006
Djokovic's family said his release was the 'biggest victory of his life'.
Wimbledon was scrapped for the first time since World War Two on Wednesday due to the coronavirus pandemic, with the suspension of professional tennis extended to July 13. The 38-year-old Federer is well insulated from the shutdown's financial fallout it could well impact his hopes of adding to his record haul of 20 Grand Slam titles.
Novak Djokovic, who won Wimbledon to take his major singles titles to 21, has opted not to be vaccinated against COVID-19. He said on Thursday he could not fly to New York for the year's final Grand Slam.
Gauff will not compete in the Tokyo Olympics after testing positive for COVID-19,
'I am very proud to pack for Tokyo and join our national team'
Novak Djokovic still feels inspired by Roger Federer and Rafael Nadal, the men's world number one tennis player has said, adding that the rivalry between the so-called 'Big Three' is a great promotion for the sport.
Roger Federer got back on track at the ATP Finals with a 7-6(2), 6-3 defeat of Italian Matteo Berrettini on Tuesday.
Switzerland's Roger Federer claimed a record-equalling sixth Australian Open title with a 6-2, 6-7(5), 6-3, 3-6, 6-1 victory over Croatia's Marin Cilic on Sunday.
Wimbledon finalists Novak Djokovic and Roger Federer are on a semi-final collision course at the US Open after they were placed in the same half of the draw.
Rafael Nadal won two Grand Slams this year -- the French Open and the US Open -- to move within one of Roger Federer's record of 20 titles.
'To be part of Team Europe together is great and if we're able to possibly share the court one more time as a doubles pairing then this would be a truly special experience for us both at this stage in our careers.'
Rafael Nadal said he was lucky to be part of an era of tennis that included Roger Federer and Novak Djokovic after the Spaniard won a men's record 21st Grand Slam title at the Australian Open to move one ahead of his two great rivals.
Indian Wells organisers said on Tuesday that world number two Novak Djokovic had been placed in the tournament's draw but it was unclear if the Serbian would be permitted to enter the United States.
was on a 21-match unbeaten run before the season came to a halt in early March, winning the ATP Cup with Serbia, an eighth Australian Open title and a fifth Dubai Tennis Championships crown.
World number one Novak Djokovic earned his 1,000th tour-level victory by beating Casper Ruud 6-4, 6-3 on Saturday to reach the Italian Open final.
Novak Djokovic posted black screenshots on his Twitter and Instagram pages with the message "Black Lives Matter", and was joined by Federer and Nadal, the other members of the "Big Three" of men's tennis.
Friday's showdown will be the 40th meeting between the duo with Rafael Nadal leading 24-15 and 10-3 in Grand Slams.
The six months off, however, appeared to be positively cathartic as he provided arguably the major talking point of the tennis circuit by reviving a career that pundits thought could be over with the injury.
World number three Roger Federer beat Romanian qualifier Marius Copil 7-6(5), 6-4 to win the Swiss Indoors on Sunday and claim his 99th career title in front of his home crowd in Basel.
World number three Roger Federer is playing his first tournament on clay for three years as he prepares for the French Open.
Stanislavskyi holds the Guinness World Record as the world's oldest tennis player
Novak Djokovic said he expects a "great battle" against Italian powerhouse Matteo Berrettini in Sunday's Wimbledon final when victory will earn the Serb a record-equalling 20th Grand Slam title.
The 21-year-old has now recorded victories over all of tennis's so called 'Big Three' this year, having beaten Roger Federer at the Australian Open and Rafa Nadal in Madrid.
Roger Federer admits he suffered a "bit of a breakdown" during last month's tour of Mexico and South America after rioting in Colombian capital Bogota forced him to cancel his exhibition match against German's Alexander Zverev.
Novak Djokovic is capable of extending his record for holding the men's World No. 1 ranking for most weeks to 400, said Russia's Daniil Medvedev who will climb up to a career-best ranking of second on Monday.
Federer displayed his trademark silky movement and said the knee had held up during a two-hour 24 minute duel.
Second seed Daniil Medvedev will launch his bid to win his first major title against veteran Frenchman Richard Gasquet.
Barcelona and Argentina striker Lionel Messi dethroned five-division boxing world champion Floyd Mayweather as the highest paid athlete over the past year.
Tsitsipas will play 22nd-seeded Spaniard Roberto Bautista Agut for a place in the semi-finals.
Novak Djokovic has declined to disclose his vaccination status despite everyone at Melbourne Park needing to be inoculated against COVID-19.
Tennis great Roger Federer sent Indian film buffs on social media into a tizzy as he asked for suggestions of Bollywood classics.
Naomi Osaka will defend her title at the US Open, organisers said on Wednesday, after she withdrew from this year's French Open and Wimbledon on mental health grounds.
France's Jo-Wilfried Tsonga is presented with an award after playing his final match before retiring REUTERS/Pascal Rossignol
Serena Williams appeared to suggest last month that she would end her playing career at the U.S. Ope
Former world number one Mats Wilander says only two things can keep Roger Federer from advancing - injury and distraction.