Melbourne (AFP) - Novak Djokovic was at the centre of another Australian Open row on Monday while defending champion Jannik Sinner needed medical attention in fierce heat to battle into the quarter-finals.

But American teenage qualifier Learner Tien’s fairytale run is over after he suffered a thigh problem in a four-set defeat to Italy’s Lorenzo Sonego.

With temperatures rising above 30 Celsius (86 Fahrenheit) for a second successive day, Ukraine’s Elina Svitolina beat Veronika Kudermetova – then declined to shake the Russian’s hand.

Five-time major champion Iga Swiatek will later be desperate to avoid a big shock against “lucky loser” Eva Lys in her bid to win a maiden Melbourne crown.

The 24-time Grand Slam champion Djokovic on Sunday refused to do a routine on-court interview after beating Jiri Lehecka to set up a quarter-final blockbuster against Carlos Alcaraz.

Afterwards he said it was in protest at Tony Jones, a top sports presenter with host broadcaster Channel Nine, who he accused of “insulting and offensive comments” towards him and Serbian fans.

Jones on Friday labelled Djokovic a “has-been”, among other things, and said: “Kick him out.”

Djokovic said he would boycott interviews with the TV station until he got an apology.

He later released a short video on X to explain his stance and it has been viewed more than 60 million times, and caught the attention of the site’s owner Elon Musk.

“It’s way better just to talk to the public directly than go through the negativity filter of legacy media,” Musk posted in response, with Djokovic replying: “Indeed.”

Tennis stars past and present and Australian Prime Minister Anthony Albanese all waded into the row.

Jones apologised on air Monday and hours later organisers Tennis Australia said: “Novak acknowledges the apology has been given in public as requested, and is now moving on and focusing on his next match.”

Djokovic has been at the centre of controversy before at the Australian Open, notably in 2022 when he was deported on the eve of the tournament over his refusal to be vaccinated against Covid.

He claimed ahead of this year’s tournament that he was “poisoned” by lead and mercury in his food while held in a hotel before being deported.

- Svitolina ‘light’ for Ukraine -

World number one Sinner needed medical attention and overcame a long interruption when he broke the net with a thunderous serve to reach the last eight.

He came home 6-3, 3-6, 6-3, 6-2 against Danish 13th seed Holger Rune on Rod Laver Arena.

Sinner struggled in the muggy conditions, his hand visibly shaking and his heart rate taken in the third set before he left court for a medical timeout.

Home hope Alex de Minaur, the eighth seed, faces Alex Michelsen of the US in a night match with Sinner awaiting the winner.

Svitolina, the 28th seed, defeated Russia’s unseeded Kudermetova 6-4, 6-1 to reach the last eight at Melbourne Park for a third time.

Svitolina refused to shake her opponent’s hand afterwards, as is the case for all Ukrainian players facing Russians because of the war.

“For me to find a way to win matches, to find a way to bring a little light, a little win for the Ukrainian people is something that I feel I am responsible for,” said the 30-year-old from Odesa.

“To bring the fight is the least that I can do.”

Organisers displayed a notice on giant screens explaining to spectators that no handshake would take place and asking for “respect in these difficult circumstances”.

Svitolina faces American 19th seed Madison Keys after she beat former finalist Elena Rybakina in three sets.

Svitolina’s husband Gael Monfils, the 38-year-old Frenchman, will aim to make it a double celebration when he faces American 21st seed Ben Shelton.

Should Monfils win he will face Italy’s Sonego after he beat the 19-year-old Tien 6-3, 6-2, 3-6, 6-2.

Tien had shocked Daniil Medvedev in a late-night five-set thriller in the second round to announce himself on the world stage.