Australian Open

  Despite the world number 114 causing moments of tension, Djokovic had enough quality to win 6-3 6-4 6-2.

The 33-year-old Serb won the final four games to finally shrug off Karatsev.

Djokovic, who is going for a record-extending ninth men's title in Melbourne, will face Daniil Medvedev or Stefanos Tsitsipas in Sunday's final.

Russian fourth seed Medvedev meets Greek fifth seed Tsitsipas in the other semi-final on Friday, with both men trying to reach their first Australian Open final.

American Williams, 39, has rediscovered her best form at Melbourne Park but faces a tough test against Osaka.

She has not played Osaka at a Grand Slam since the Japanese beat her in a dramatic 2018 US Open final.

The match was overshadowed by Williams' argument with umpire Carlos Ramos.

Williams called the umpire a "thief" after he deducted a point from her, and Osaka was reduced to tears by the crowd booing during the presentation ceremony.

"I think we both have had closure, and we have reached out to each other," Williams said of the match.

The 39-year-old went toe-to-toe with the Romanian second seed over 80 minutes on Rod Laver Arena before she was finally able to move to within two victories of a record-equalling 24th Grand Slam title.

Williams hit some ferocious forehands and moved around the court with a freedom that she has not enjoyed for a good while to set up a semi-final meeting against in-form Japanese third seed Osaka.

Barty overcame a stumbling start to claim a 6-2 6-4 victory over Ekaterina Alexandrova at an empty Margaret Court Arena on Saturday.

The 24-year-old would have expected the backing of a fiercely partisan crowd for a weekend evening match at her home Grand Slam, but Melbourne's five-day lockdown left her playing in front of officials, ballkids and coaches.

While most other players have seen plenty of empty courts on the WTA tour over the last year, it was a new experience for Barty, who elected to stay home while the COVID-19 pandemic raged around the world.

Stojanovic had her moments, especially in the first set, before being inevitably overpowered by the No 10 seed in 69 minutes.

The 24-year-old Serb had claimed her maiden win at a major two days earlier against Romanian Irina-Camelia Begu.

"She pushed me really hard and played really well honestly throughout the whole match," said the 39-year-old Williams.

"I had to really fight for all the games.

"It's always good to see young players like her come out and do so well - it's exciting for women's tennis."

Wearing a colorful one-legged catsuit that she said was inspired by former Olympic sprint champion Florence Griffith Joyner, Williams shook off a wobbly start – opening with a double-fault and dropping her first service game – to sweep 10 consecutive games and beat Laura Siegemund 6-1, 6-1 on the first day of the tournament.

The victory marked the start of Williams’ latest bid for a record-tying 24th major title. As she left the court she flexed her biceps, and later she donned a T-shirt that read “Unstoppable Queen.”

Triple Grand Slam champion Osaka said it had taken time to get used to the system but would be happy for it to be adopted at other tournaments.

"I feel like for me, it saves me the trouble of attempting to challenge or thinking about, 'Did they call it correctly or not?'" the Japanese third seed said.

"It actually gets me really focused. I don't mind it at all."

The Australian Open is the first Grand Slam to dispense with human line judges as part of efforts to reduce personnel and stage a biosecure tournament amid the Covid-19 pandemic.

Thursday's play at the six warm-up events at Melbourne Park has been cancelled as a result.

But Victoria Premier Daniel Andrews said: "At this stage there is no impact on the tournament proper."

Players will be free to return to competition after a negative test.

"We will work with everyone involved to facilitate testing as quickly as possible," said Australian Open organisers.

The Grand Slam tournament, which was pushed back by three weeks to enable players to quarantine, starts on Monday.

The first group among the 960 players, coaches and officials isolating at three Melbourne hotels were allowed to leave, with the rest expected to depart by Sunday, Victoria state health officials said.

Players isolating in South Australia state, including Novak Djokovic and Serena Williams, were also to be released ahead of an exhibition tournament in Adelaide on Friday.

Players will be free to move around the cities and surrounding regions so long as they abide by local social distancing restrictions.

Victoria health officials said two previous cases have been classified as prior infections taking the total positive cases associated with the tournament to seven.

"The new positive cases linked to the Australian Open involve two players and one non-playing participant," said a statement from the health department.

Tiley said athletes who tested positive were not considered contagious and were still at their regular accommodation.