Roger Federer has downplayed suffocating heat on court at the Australian Open, saying it was part of the game and players should be prepared.
The Swiss great was commenting on furnace-like conditions at Melbourne Park on Thursday, which his rival Novak Djokovic described as "brutal", complaining it was hard to breathe.
More of same was expected Friday, with a peak of 42 Celsius (107.6 Fahrenheit) forecast.
Federer escaped the worst on Thursday, playing a night match on Rod Laver Arena, but said he had played in searing Australian temperatures plenty of times and experienced worse.
"If you want to get to the top, you've got to play in all conditions," he said.
"We know it can be very hot here in Australia. I remember the days when we had four days of 40 degrees in a row a few years back. Now we got two.
"It's definitely a challenge," he added. "It's hard to prepare for that in some ways. But you know when you come down here that can happen.
"Sure, I was watching the other players suffer. As long as nothing bad happens, it's all good."
Among those in trouble was Gael Monfils, with fears for his health in his mid-afternoon match against Djokovic.
The Frenchman, known as one of the fittest players on tour, looked dazed and confused in the second set and eventually got medical assistance.
He said afterwards he was "dying" on court.
Organisers will only active the extreme heat policy when the temperature exceeds 40 Celsius and the wet bulb globe temperature index hits 32.5 Celsius, which means matches could be affected Friday.
Federer said it was a tough call to make.
"What do you do? You stop all matches?," he asked.
"The lucky guys on the big courts, they get to play under the roof. The other guys get postponed till the next day? Is that great? That's not great either."
He added that all the players knew these conditions could happen.
"Everybody has to face the similar issues," he said.
One of the worst years for heat at the Open was 2014, when many players were in trouble.
Among them was Blaz Kavcic who was placed on a drip, and Frank Dancevic who said was hallucinating about cartoon character Snoopy in his dazed state.
A cooler change is expected to blow through Melbourne from Saturday.