Maria Sharapova battled through 40-degree heats to reach the third round of the Australian Open after a three hour and 28 minute marathon match against Karin Knapp.
After play was stopped on the outside courts, Sharapova outlasted Knapp 10-8 in the third set which lasted 115 minutes alone.
The Russian was pushed to the limit as on-court temperatures rose to 42.4 degrees and Knapp of Italy held firm before Sharapova prevailed to set up a round three encounter with Alize Cornet.
"There is no way of getting around the fact that the conditions were extremely difficult, and have been for the last few days," said the Russian.
"It's a tough call. The question I have is no-one really knows what the limit is - not the players or the trainers when you ask them if the roof will be closed.
"No-one actually knows what that number is in comparison to humidity or the actual heat. I asked the trainer the other day what it takes for the roof to be closed or matches to be stopped, and she said 'we have no control over this'."
No.1 seed Rafael Nadal beat Australian Thanasi Kokkinakis in straight sets as did Roger Federer who overcame Blaz Kavcic as both players cruised into round three.
In the doubles, Britain's Jamie Murray and his partner John Peers of Australia won their opening match to progress to the second round.
Federer, who beat Slovenian Blaz Kavcic 6-2 6-1 7-6 (7-4), took the first set in just 26 minutes and it begun a blitz from the 17-time major winner.
Kavcic then fought back in the third taking it to a tie-break but Federer proved too strong and progresses to the next round where he will face Spaniard Fernando Verdasco.
Nadal meanwhile thrashed Australian Thanasi Kokkinakis 6-2 6-4 6-2.