Jannik Sinner put his third-round drama behind him to ease into the quarter-finals of the Australian Open.

Two days after the two-time defending champion cramped badly against Eliot Spizzirri and was saved by the closing of the Rod Laver Arena roof, Sinner defeated compatriot Luciano Darderi 6-1 6-3 7-6 (2).

He has never lost to a fellow Italian at tour level, extending his winning record to 18-0 and it was not until the third set that Darderi offered any substantial resistance.

The 22nd seed possesses a powerful forehand and saved two match points at 5-4 before taking an early lead in the tie-break but Sinner responded emphatically, winning seven points in a row.

Sinner, who also served a grand slam career-best 19 aces, said: “It was very, very difficult. We are very good friends off the court.

“I felt like in the third set I had a couple of break-point chances, couldn’t use them and then it got very, very tight. I’m very happy.

“We put a lot of work in, especially with the serve. We changed a bit the motion and I feel for sure a little bit more confident. I’m very happy how I’ve come back in the new season.”

Lorenzo Musetti made it two Italians into the last eight with a 6-2 7-5 6-4 victory over a struggling Taylor Fritz to set up a clash with Novak Djokovic, who had the day off after scheduled opponent Jakub Mensik withdrew on Sunday citing an abdominal problem.

It is a third grand slam quarter-final out of the last four majors for Musetti, who could go as high as three in the rankings after this tournament.

Meanwhile Jessica Pegula knocked podcast pal and defending champion Madison Keys out yesterday to secure a quarter-final against Amanda Anisimova, another all-American match.

Their fourth-round wins on Day 9 means four Americans have reached the women’s singles last eight in Australia for the first time since 2001, when Serena and Venus Williams, Jennifer Capriati, Monica Seles and Lindsay Davenport made it through.

It is also the first time the top six seeds in the women’s and men’s singles have all qualified for the last eight of a Grand Slam event in the Open Era.

Things were certainly heating up today — and will continue to do so on Tuesday as the Australian Open organisers have had to make changes to the schedule because of extreme heat for the second time in four days.

After the start of play was brought forward on Saturday, action was due to begin on outside courts this morning at 9am, while the start of the wheelchair competitions has been delayed until tomorrow.

Play was suspended on uncovered courts for almost five hours on Saturday after the tournament’s heat stress scale — which takes into account air temperature, radiant heat, humidity and wind speed – reached the cut-off mark of five.

The roofs were used on the three main show courts – Rod Laver, Margaret Court and John Cain arenas – and the same outcome is likely on Tuesday, with temperatures forecast to be even hotter, and potentially up to around 46°C by 5pm.

World number one Aryna Sabalenka is scheduled first on Rod Laver at 11.30am against US teenager Iva Jovic, with Alexander Zverev’s clash with Learner Tien following not before 1.30pm.

It was that slot that two-time defending champion Jannik Sinner played in on Saturday and struggled with cramp before the roof closed.

Ball boys and girls will spend less time on court and have more time in between stints, while tournament organisers have warned spectators to prepare for the conditions and stay hydrated.