MELBOURNE — Defending champion Jannik Sinner needed medical attention in energy-sapping heat and overcame a long interruption when he broke the net to reach the Australian Open quarterfinals on Monday.

The top seed again dropped a set before coming home 6-3, 3-6, 6-3,6-2 against dangerous Dane Holger Rune at Rod Laver Arena with both men needing medical attention.

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.

Rune needed attention to a sore right knee in the same set.

They then had a bizarre 20-minute delay when Sinner demolished the metal brace that secures the net to the floor with a thunderous serve early in set four.

"It was for sure very, very tough," said Sinner, who is bidding to become the first Italian man to win three Grand Slam crowns.

"I tried to stay there mentally, I tried to stay connected with my service game and in my return game just seeing what happens."

Asked what his medical problem was, he was evasive.

"I had a strange morning because I didn't warm up today," he replied. "I knew in my mind already that I would struggle today."

The Italian is bidding to defend a Grand Slam title for the first time after winning the first of his two majors in Melbourne last year, beating Daniil Medvedev in the final.

It was the catalyst for a sensational year that saw him win eight titles, including the US Open and ATP Finals and his victory over 13th seed Rune extended his win streak to 18 matches.

The 23-year-old stamped his authority on the match immediately by breaking to love, with Rune hitting four consecutive errors.

Sinner's serve was iron-clad and there was no sniff for the Dane, who went one set down in 33 minutes.

But a Sinner double-fault in the eighth game of the second set handed Rune a break, allowing him to hold and level the match as he began to find his rhythm.

It was the second set Sinner had dropped in the tournament, having not done so in 13 previous matches.

Sinner clung on to hold in an epic game three in the third set, which included a remarkable 37-shot rally that the Italian won to save a break point.

He gave Rune another break point at 2-2 with a double fault, again saving, but he was laboring.

At the changeover, a doctor checked him and he went off for a medical timeout.

Sinner returned and slogged through a testing 14-point eighth game to break for 5-3 before sealing the set.

After the delay while the net was fixed, he produced a top-notch forehand winner to break for 2-1 in the fourth set and there was no way back for a tiring Rune.

Compatriot Lorenzo Sonego ended the dream run of another teenager at the Australian Open as the unseeded Italian beat qualifier Learner Tien 6-3, 6-2, 3-6, 6-1 and reached the quarterfinals of a Grand Slam for the first time on Monday.

Sonego had taken out Brazilian 18-year-old Joao Fonseca in the second round and his experience proved crucial yet again as he ground out the win over 19-year-old American Tien at John Cain Arena.

"I don't know what to say. It's just unbelievable, I'm crazy emotional," said 29-year-old Sonego. "Today was so tough, I'm so sad that he had a problem. It's not the right way to win, but I'm so happy to reach the quarterfinals.

"The atmosphere was amazing, it was really special to be here. I want to do my best and I played well this week. I want to enjoy every moment," added Sonego, a singer-songwriter in his spare time with a notable presence on Spotify.

In the women's play, Elina Svitolina was 4-1 down before she went on a roll and took 11 of the next 12 games in a 6-4, 6-1 victory over Veronika Kudermetova on Monday to reach the quarterfinals for the third time.

The 30-year-old Ukrainian is into the last eight at a Grand Slam for the 12th time and will next play No 19 Madison Keys, who had a 6-3, 1-6, 6-3 win over Elena Rybakina, the 2022 Wimbledon champion and 2023 Australian Open runner-up.

Keys has twice reached the semifinals in Australia, in 2015 and 2022, and entered the season's first major with a title in Adelaide earlier this month.

Agencies