MELBOURNE, Australia (AFP) — Jessica Pegula sent reigning champion and podcast co-host Madison Keys spinning out of the Australian Open on Monday while Jannik Sinner aims to avoid the same fate and reach the quarterfinals in stifling heat.

In temperatures approaching 30C in Melbourne, fifth seed Lorenzo Musetti set up a “Last Eight” showdown with Novak Djokovic.

Keys and Pegula launched day nine in a clash at Rod Laver Arena between two Americans who know each other well.

They are good friends and also host a tennis podcast together, "The Player's Box," and had even been planning to record an episode on the eve of their match.

All that was put aside as a clinical Pegula dominated 6-3, 6-4 to set up a quarterfinals encounter with another American in fourth seed Amanda Anisimova.

Anisimova, beaten finalist at last year's US Open and Wimbledon, cooled herself off with bags of ice before taming China's Wang Xinyu 7-6 (7/4), 6-4.

Pegula, the 31-year-old sixth seed, is chasing an elusive Grand Slam title, her best performance to date reaching the US Open final in 2024.

An erratic Keys made 27 unforced errors to Pegula's 17 and fired down six double faults as her title defence ended in the last 16.

The forfeit, as a part of a jokey bet with Pegula, will be a slice of apple pie with melted cheddar cheese on top.

"A bet is a bet, so I'll do it. I hope it's less gross than I think it's going to be, but we will find out," said Keys, who described herself as proud despite defeat.

Also in the women's draw in the fourth round, fifth seed Elena Rybakina plays 21st seed Elise Mertens of Belgium.

Second seed Iga Swiatek will be heavy favorite against Maddison Inglis.

Australian qualifier Inglis, ranked 168, features on Rod Laver Arena in the biggest match of her life.

The 28-year-old was given free passage into the last 16 when two-time Melbourne champion Naomi Osaka pulled out injured.

After sizzling weather caused the suspension of matches on Saturday, temperatures are rising sharply again.

Longer matches on Monday will have 10-minute breaks in certain circumstances as part of measures to protect player health.

Temperatures are forecast to hit a blistering 44C on Tuesday, meaning matches are likely to be played under roofs on the three courts that have them.

Later Monday, reigning champion Sinner — who struggles in the heat — will be strong favorite against fellow Italian Luciano Darderi.

Darderi, the 22nd seed, has never made it this far at a Grand Slam while Sinner is chasing a third Australian Open crown in a row.

Only Djokovic has done that in the Open era.

Melbourne Park king Djokovic was supposed to play the 20-year-old Jakub Mensik in a night match.

But the Czech player pulled out injured on Sunday, sending 10-time champion Djokovic into the last eight without hitting a ball.

The 38-year-old Serb will play Musetti after the Italian defeated American ninth seed Taylor Fritz 6-2, 7-5, 6-4.

In the last match of the day on center court, United States eighth seed Ben Shelton plays Norway's 12th seed Casper Ruud in the timeslot when Djokovic was supposed to be on court.