Carlos Alcaraz faces having to beat not just Alex de Minaur but also a patriotic home crowd to make his first Australian Open semifinal on Tuesday, when a freak heatwave is set to send temperatures soaring towards 45C.
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Four quarterfinals are on day 10 at Melbourne Park, with all of them set to take place under the roof of Rod Laver Arena because of the forecast extreme heat.
Play on outside courts, where doubles action is scheduled, is likely to be affected.
German third seed Alexander Zverev, who lost the final last year to Jannik Sinner, is also in action, meeting American next-gen star Learner Tien.
Whoever comes out on top will meet top seed Alcaraz or sixth seed De Minaur for a place in Sunday's decider.
"If it is going to be really, really hot on Tuesday and the roof is going to be closed, I got to accept that and just try to play my best tennis indoors," said Alcaraz.
"So whatever it is, I just will be ready. I will be focused. I will try not to think about it. I will try not to let it affect my game at all."
The Spanish 22-year-old has won six Grand Slams, but is yet to go past the last eight in Melbourne.
De Minaur has failed to make it past the quarterfinals at any Slam and is hoping the home fans can help him pull off an upset in the last match of the day on centre court.
"For me, it just comes down to I'm going to have to bring some of my best tennis," said the Australian, who has lost all five previous encounters with Alcaraz.
"Once I rock up on Tuesday and I walk on court, you just deal with whatever's in front of you," he added of the roof likely being closed.
Two-time women's champion Aryna Sabalenka opens the action on Rod Laver Arena against exciting American teenager Iva Jovic, who stunned two-time Grand Slam finalist and seventh seed Jasmine Paolini in round three.
Jovic, 18, annihilated the experienced Yulia Putintseva 6-0, 6-1 in her previous match and said she has no fear of four-time major winner Sabalenka.
"I don't really feel like there is a lot of house money or underdog mentality that I'm feeling," said the 29th seed.
Sabalenka, the 2023 and 2024 champion, lost the final last year to Madison Keys, who was knocked out of the tournament on Monday by Jessica Pegula.
The winner will meet either American third seed Coco Gauff or 12th-seeded Ukrainian Elina Svitolina.
That quarterfinal will precede Alcaraz and De Minaur on Rod Laver Arena in the evening session.