MELBOURNE, Australia — On a day when shade was a valuable commodity in the searing heat at Melbourne Park, Roger Federer played it cool at the Australian Open.
Six-time champion Novak Djokovic, however, complained about the brutal conditions, which peaked at 40 degrees Celsius (104 degrees Farenheit) during his second-round win over Gael Monfils, 4-6, 6-3, 6-1, 6-3.
Djokovic urged tennis organizers to be more flexible about the rules for drink breaks, time between points and suspension of play when the conditions were bordering on dangerous.
Federer, the defending champion, finished off a 6-4, 6-4, 7-6 (4) win over Jan-Lennard Struff a half-hour before midnight, when the temperature was still around 29 degrees C (84 degrees F), and said playing at the height of the heat wouldn’t have bothered him.
‘‘I may have thrived in those conditions,’’ he said.
Stan Wawrinka, the 2014 Australian Open champion, No. 7 David Goffin and No. 13 Sam Querrey didn’t make it through the second round. Nor did Wimbledon champion Garbine Muguruza, one of the five seeded women’s players who were eliminated on Day 4.
That left only Maria Sharapova and Angelique Kerber — who will meet in the next round — and French Open champion Jelena Ostapenko as Grand Slam winners in the women’s draw.
Sharapova beat 14th-seeded Anastasija Sevastova 6-1, 7-6 (4) to avenge a loss in last year’s U.S. Open, the five-time major champion’s first Grand Slam after returning from a 15-month doping ban.
Kerber, the 2016 Australian Open champion, had a 6-4, 6-1 win over Donna Vekic before the crowd sang ‘‘Happy Birthday’’ on her 30th birthday.
Still looking for a first major, top-ranked Simona Halep held off 2014 Wimbledon finalist Eugenie Bouchard 6-2, 6-2.