Maria Sharapova survived a three-and-a-half hour struggle with Italian Karin Knapp in oppressive heat at Melbourne Park, forced to play through temperatures of 42.4 degrees.
Soaring temperatures forced matches at the Australian Open to be suspended after the tournament referee applied the extreme heat policy at Melbourne Park at 1.52pm.
But under the policy's guidelines, matches would only be suspended at the end of the set in progress.
When temperatures eclipsed 42 degrees, tournament referee Wayne McEwen deemed conditions unsafe for players, with all matches on the non-roofed courts suspended until at least 5pm.
Despite most other matches being suspended, Sharapova and Knapp were locked in a gruelling third-set battle to decide the outcome of the second-round clash and played on for another 48 minutes after the heat policy was implemented.
The third set went for an incredible 114 minutes and was the longest match Sharapova has played in 42 grand slam appearances, eventually claiming a 6-3, 4-6, 10-8 victory in three hours and 28 minutes.
"I think both it was [both mental and physically exhausting]," Sharapova said.
"It's tough for both of us. We fought as hard as we could, both of us had so many chances. She played some of the best tennis I've seen her play."
Matches interrupted because of the extreme heat policy include Jo-Wilfried Tsonga's match against Thomaz Bellucci and Andreas Seppi versus Donald Young. The Tsonga-Bellucci match restarted when the roof was closed on Hisense Arena at the conclusion of the second set.
All matches on the outside courts have been suspended until at least 5pm, while the next match on Rod Laver Arena - Caroline Wozniacki against Christina McHale - will be played under the roof.
The extreme heat policy is applied when the Wet Bulb Globe Temperature exceeds a predetermined threshold, allowing the tournament referee to suspend play at his discretion.
Given the extreme heat in Melbourne, women in the singles draw were already allowed a 10-minute break between the second and third sets and ice vests are provided on all courts.
Earlier, tournament referee Wayne McKewen said while conditions so far this week had not warranted the extreme heat policy to be implemented, “today may be a different story based on forecasts”.
Speaking to Melbourne radio station 3AW, Mr McKewen said weather conditions were being “continually re-assessed” and that he was in regular contact with the tournament's chief medical doctor and the Bureau of Meteorology, which has set up a temporary base at Melbourne Park.
The forecast top for Melbourne on Thursday is 44 degrees. Friday is expected to reach 42 ahead of a gusty change.
“We've got staff in the tournament control who are continually monitoring the weather conditions,” he said, adding that ambient air temperature, humidity and wind variation were all considered.
Mr McKewen said he was confident the regulations protected players' health and safety, despite removing the phrase “predetermined threshold” from the tournament's heat policy earlier in the week.
“I've got guidelines which I follow,” he said. “We don't want to have a hard mark as to, ok if it hits this we stop play.
"Because we all know in Melbourne temperatures can fluctuate very quickly, and if we know it's going to cool down in the next half an hour or so we'll push through that period and then continue on into the cooler period. But if I know the temperatures will spike I would rather bring everyone in earlier rather than later.”