Roger Federer fought off the challenge of Jan-Lennard Struff to move into the third round of the Australian Open.
The defending champion benefited from playing in the relative cool of the evening unlike possible semi-final opponent Novak Djokovic and emerged an ultimately comfortable 6-4 6-4 7-6 (7/4) winner.
But German Struff, ranked 55, caused a few problems for the second seed, particularly in the third set. He broke the Federer serve for the first time this tournament to lead 3-1 but back came the Swiss to clinch victory in a tie-break.
Federer, who next faces Frenchman Richard Gasquet, said: "I knew he was going to go for his shots, it's a question of protecting your own serve as well as you can, then try to get a break. I thought it was a good match, I enjoyed it."
The 36-year-old revealed he did ask to play at night having played his first-round match late but said he would have been happy to play during the day.
"There's maybe 60 guys asking for different things and I'm one of them," he said with a sheepish grin. "It's their call. I'm happy I didn't have to go from night to day, I'm happy to play in the same rhythm.
"I wouldn't have minded playing in the day because I like to think I thrive in those conditions. If you want to get to the top you have to play in all conditions." 181259 JAN 18
Djokovic believes players were asked to push their physical limits after opponent Gael Monfils complained of suffering heat-stroke.
The thermometer edged towards 40C in the shade as Djokovic and Monfils took to a sun-baked Rod Laver Arena for their second-round match, which the six-time champion eventually won 4-6 6-3 6-1 6-3.
Monfils began to really suffer during the second set, repeatedly doubling over and not even attempting to return serve during one game.
The Frenchman rated the conditions the toughest he has ever played in, saying: "For sure, we took a risk. I got super dizzy. I think I had a small heat-stroke for 40 minutes. I tried to cool down. But even with the ice towel, the water, I think my body was super warm."
The Australian Open has an extreme heat policy but it does not come into effect until the temperature hits 40C, while a decision on whether play continues also depends on the humidity.
Monfils argued there should be leeway for players to take longer between points than the allotted 25 seconds and for longer breaks between sets when conditions are so physically challenging.
And Djokovic, who is reportedly behind the idea of forming a separate players' union, made a plea for the health of the players to be put first.
He said: "You work and train hard to be able to sustain these kind of conditions, to be tough. But I think there is a limit, and that is a level of tolerance between being fit and being in danger in terms of health. It was right at the limit.
"Our sport has become an industry, like most of the other global sports. It's more business than a sport. At times, I don't like that. What is most important for us is our health and what happens after our career, after you're 30, 35. There are many players that are struggling."
Fifth seed Dominic Thiem showed tremendous mental and physical resilience to defy the conditions and come from two sets down to beat Denis Kudla 6-7 (6/8) 3-6 6-3 6-2 6-3.
There was a big shock on Show Court 2, where seventh seed David Goffin was beaten 1-6 7-6 (7/5) 6-1 7-6 (7/4) by French veteran Julien Benneteau, who is playing at Melbourne Park for the final time.
Juan Martin del Potro was also tested but defeated Russian Karen Khachanov 6-4 7-6 (7/4) 6-7 (0/7) 6-4.
Meanwhile, Stan Wawrinka's comeback tournament ended with a second-round loss to Tennys Sandgren at the Australian Open.
The 2014 champion was back in action for the first time since Wimbledon after undergoing surgery on his left knee and only decided that he would definitely play on Saturday.
After pulling out of all his scheduled warm-up events, Wawrinka sounded decidedly pessimistic about his chances but fared better than expected in a first-round victory over Ricardas Berankis.
However, he never looked comfortable against American Sandgren, ranked 97, and lost comprehensively 6-2 6-1 6-4.
Of more concern was the degree of pain Wawrinka seemed to be feeling in his knee, with the 32-year-old wincing and flexing the joint, which bears a large scar.