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 during his 4-6, 6-3, 6-1, 6-3 second-round win over Gael Monfils, when the temperature peaked at 104 degrees Fahrenheit.

Djokovic, saying the conditions were some of the toughest in which he’s ever played, urged organizers to be more flexible about the rules for drink breaks, time between points and suspension of play when the conditions were at the point where it becomes a “danger in terms of health.”

“There are certain days where you just have to, as a tournament supervisor, recognize that you might need to give players a few extra hours,” he said. “I understand there is a factor of tickets. If you don’t play matches, people will be unhappy.”

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 84 degrees.

Temperatures are expected to rise Friday, before cooling off considerably over the weekend, when Federer and Djokovic’s half of the draw is back for the third round.

Stan Wawrinka, the 2014 Australian Open champion returning from a six-month layoff after knee surgery, No. 7 David Goffin and No. 13 Sam Querrey didn’t make it through the second round. Nor did Wimbledon champion Garbiñe 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.

John Pye is an Associated Press writer.

Thursday’s seeded results

Men’s second round: Winners — No. 2 Roger Federer beat Jan-Lennard Struff 6-4, 6-4, 7-6 (4); No. 4 Alexander Zverev beat Peter Gojowczyk 6-1, 6-3, 4-6, 6-3; No. 5 Dominic Thiem beat Denis Kudla 6-7 (6), 3-6, 6-3, 6-2, 6-3; No. 12 Juan Martin del Potro beat Karen Khachanov 6-4, 7-6 (4), 6-7 (0), 6-4; No. 14 Novak Djokovic beat Gael Monfils 4-6, 6-3, 6-1, 6-3; No. 19 Tomas Berdych beat Guillermo Garcia-Lopez 6-3, 2-6, 6-2, 6-3; No. 21 Albert Ramos-Vinolas beat Tim Smyczek 6-4, 6-2, 7-6 (2); No. 25 Fabio Fognini beat Evgeny Donskoy 2-6, 6-3, 6-4, 6-1; No. 26 Adrian Mannarino beat Jiri Vesely 6-3, 7-6 (4), 5-7, 6-3; No. 29 Richard Gasquet beat Lorenzo Sonego 6-2, 6-2, 6-3. Losers — Julien Benneteau beat No. 7 David Goffin 1-6, 7-6 (5), 6-1, 7-6 (4); Tennys Sandgren beat No. 9 Stan Wawrinka 6-2, 6-1, 6-4; Marton Fucsovics beat No. 13 Sam Querrey 6-4, 7-6 (6), 4-6, 6-2.

Women’s second round: Winners — No. 1 Simona Halep beat Eugenie Bouchard 6-2, 6-2; No. 6 Karolina Pliskova beat Beatriz Haddad Maia 6-1, 6-1; No. 8 Caroline Garcia beat Marketa Vondrousova 6-7( 3), 6-2, 8-6; No. 17 Madison Keys beat Ekaterina Alexandrova 6-0, 6-1; No. 18 Ashleigh Barty beat Camila Giorgi 5-7, 6-4, 6-1; No. 20 Barbora Strycova beat Lara Arruabarrena-Vecino 6-3, 6-4; No. 21 Angelique Kerber beat Donna Vekic 6-4, 6-1; No. 26 Agnieszka Radwanska beat Lesia Tsurenko 2-6, 7-5, 6-3; Losers — Hsieh Su-Wei beat No. 3 Garbiñe Muguruza 7-6 (1), 6-4; Bernarda Pera beat No. 9 Johanna Konta 6-4, 7-5; Maria Sharapova beat No. 14 Anastasija Sevastova 6-1, 7-6 (4); Naomi Osaka beat No. 16 Elena Vesnina 7-6 (4), 6-2; Aliaksandra Sasnovich beat No. 28 Mirjana Lucic-Baroni 6-3, 6-1; No. 29 Lucie Safarova beat Sorana Cirstea 6-2, 6-4.