Jannik Sinner admitted he was "playing against himself a little bit" as he battled with illness during his win over Holger Rune in the Australian Open fourth round.

The Italian prevailed 6-3 3-6 6-3 6-2 in the Melbourne heat on Monday but had to take an 11-minute medical time out in the third set before a net malfunction caused further delay at the start of the fourth.

However, Sinner kept his Australian Open title defence on track as he dug deep to beat the Dane and reach his 10th grand slam quarter-final.

Excluding the ATP Finals (which only includes eight players), the world number one has reached the quarters at the last 15 ATP-level events he has competed in, dating back to last year's Australian Open. The only other players to achieve that in the last 30 years have been Roger Federer, Novak Djokovic and Rafael Nadal.

Sinner admitted it was a tough match for him as he struggled with illness but was pleased to get over the line at Rod Lavar Arena.

"I don't want to talk so much [about] how I felt today," Sinner said. "I was not feeling really well.

"I think we saw that today I was struggling physically. Came here as late as possible. I knew that it was going to be very, very difficult today.

"Playing against a tough opponent but also playing against myself a little bit. I knew this before. I tried to handle the situation on the court as good as I could, which I think today I handled as well as possible. [I'm] happy to be in the next round."

15 - Jannik Sinner is the fourth player in the last 30 years to reach the quarter-finals for 15 consecutive Tour level tournaments (ATP Finals excluded)

Roger Federer
Rafael Nadal
Novak Djokovic
Jannik Sinner

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When asked about his medical timeout in the third set, Sinner added: "I talked with the doctor before already, before going on the court. I had a little checkup. It was a bit helpful. I at least felt slightly better when I went back on court.

"I felt like the face looked a little bit better, the colour was a little bit back. It helped for sure. It's tough conditions.

"When you're not there health-wise where you want to be, it's also even more difficult, but it helped, yeah. It gave me some small medication, and then it was slightly better."

As for Rune, he has now won just one of his last 10 grand slam matches against opponents ranked in the top 10, with his sole victory coming against Stefanos Tsitsipas at the French Open in 2022.

The two delays in the match broke up the momentum after Rune had fought back to level the score in the second set, and he struggled to regain his rhythm.

"It was a very warm day today, even though there was not sun the whole time," Rune said. "It was very humid, so I was also feeling it. It's fair that he got checked.

"I think it took longer than I expected. It was around ten minutes, maybe even more. So that was a bit brutal in the middle of the set. Again, it is what it is. I just couldn't move on.

"I had good momentum in this moment. So, yeah, it was not the worst timing from his side.

"I think first set he played great. Second set I was playing good. So it was, like, first set he was better than me. Second set I was better. Third set, up until he took the medical time-out it was really a battle. We had long rallies.

"We had this incredible game with sick rallies. It was really, really tough. I mean, I was almost dying, also. It was really a struggle. I could see he was also struggling. So, it's normal.

"It was, as I said, definitely very, very humid, very warm today. Like sticking a lot on the body. Especially having around a 10-12 minute break, just sitting in the heat for me cooking out there is a bit tough.

"It is what it is, as I have said. Just had to move on and maybe be smarter next time to wait off-court. Yeah, it was a bit too long."