Holger Rune has renewed calls for a universal heat rule and Novak Djokovic required treatment as players fought through brutal conditions at the Shanghai Masters on Tuesday.
Rune, the world number 11, was heard to ask "do you want a player to die on court?" during his victory over Ugo Humbert on Sunday, 6-4, 6-7 (7), 6-3 victory over Giovanni Mpetshi Perricard.
"We can handle a certain amount of heat, because we're strong, and mentally strong as well, but there is always a limit," he told reporters after the match.
"It's also important to take care of your health. We need to survive."
Djokovic, 38, had to take a medical timeout after picking up a leg injury during the first set of an encounter against Jaume Munar that stretched to two hours and 41 minutes.
Djokovic won 6-3 5-7 6-2, but struggled with the heat.
Medics checked his vital statistics at one point as the temperature stayed near 30 degrees Celsius and humidity hovered at about 80 per cent.
The Serbian vomited during his match against Yannick Hanfmann on Sunday and world number two Jannik Sinner retired due to cramps.
"It's the same for every player out on the court, but it's brutal," Djokovic said after beating Hanfmann 4-6, 7-5, 6-3.
"It's brutal when you have over 80 per cent of humidity day after day, particularly for the guys when they're playing during the day with heat, with sun, it's even more brutal."
Fourth seed Djokovic, who had got the first break of the match to go 3-1 up in the opening set before he hurt his leg, could not break Munar's serve during the second set, which the world number 41 won after a 75-minute battle.
The 24-time grand slam winner bent over in exhaustion and needed more medical attention before clinching the decisive third set with two well-timed breaks.
Djokovic collapsed on the court after winning the match.
He is set to face Zizou Bergs in the last eight.
Earlier on Tuesday, Emma Raducanu retired from her Wuhan Open match against Ann Li after struggling with exhaustion and having her blood pressure checked on a hot and humid afternoon.
Iga Swiatek enjoyed a 6-1 6-1 rout of Marie Bouzková, but noted that conditions the day prior would have been "too much for most of the players".
"I hope the other matches will be scheduled at a time where girls can compete, rather than just die on the court," Swiatek said.
The ATP said it would consider introducing a formal heat rule, as was the case at the Australian Open and other grand slams.
"Every player would agree," that a heat rule should be implemented, Rune said.
In a statement, the ATP said player safety was its highest priority and that on-site medical teams monitored the conditions.
De Minaur focuses on 'surviving'
Meanwhile, seventh-seeded Alex De Minaur defeated Kamil Majchrzak 6-1, 7-5 in humid conditions for his tour-leading 36th win on hard courts this year.
The 26-year-old broke Majchrzak's serve five times to reach the Masters 1000 fourth round for the seventh time this season.
Two of the breaks came after he dropped serve to trail 4-3 in the second set.
"I came into this week knowing how tough the conditions were going to be," De Minaur said.
"So the mindset, ultimately, is surviving, finding ways and getting ready for battles every time you step out on the court.
"There is no such thing as easy matches, especially in these conditions, so I'm glad I was able to compose myself in the second set, get the break back, and finish it off in two.
"If we had gone into a third, it would have been very physical."
De Minaur will next face Nuno Borges, who defeated Shang Juncheng 7-6 (5), 4-6, 6-3.
Another win for De Minaur would see him hit 50 tour-level victories in a season for the first time.
Wires/ABC
