World No. 1 Iga Swiatek spearheaded the women's seeds' march into the final 16 of the Australian Open on Friday, as organizers staunchly defended what Andy Murray had branded a "farce" of a 4:05 a.m. conclusion.

The Americans Coco Gauff and Jessica Pegula were also big winners, ensuring that regular order was resumed on day five at Melbourne Park following the shocks of a day earlier.

World No. 2 Ons Jabeur was the biggest casualty in the women's draw on Thursday, while the men's field has lost its top two seeds Rafael Nadal and Casper Ruud.

Hot favorite Swiatek, a three-time major winner but chasing a first Australian Open title, swatted aside qualifier Cristina Bucsa of Spain 6-0, 6-1.

The Pole faces Elena Rybakina next after the Wimbledon champion defeated last year's Melbourne runner-up Danielle Collins in three sets.

"For sure, she's solid physically and mentally," Moscow-born Kazakh Rybakina said, eyeing up the Swiatek challenge.

"I will have to take all my chances. I think Iga is a great player."

The 18-year-old Gauff stepped up her bid for a maiden major title with a similarly emphatic 6-3, 6-2 victory over fellow American Bernarda Pera.

The talented teenager faces the 2017 French Open champion Jelena Ostapenko of Latvia in the last 16.

Third seed Pegula, who is also chasing a first Grand Slam crown, also did light work of Marta Kostyuk with a 6-0, 6-2 victories.

The 28-year-old next faces what should be a sterner test in Barbora Krejcikova of the Czech Republic, the 20th seed and 2021 French Open champion.

Bit of a farce

Off the court, Australian Open chief Craig Tiley insisted there was "no need" to alter the scheduling, despite stinging criticism after the second-latest finish at a Grand Slam.

Veteran Murray battled through a five-set epic against home hope Thanasi Kokkinakis, which ended at 4:05 am, calling the early hours conclusion "a bit of a farce."

"I don't know who it's beneficial for. A match like that, we come here after the match, and that's what the discussion is," the 35-year-old Briton said after the five hours and 45 minutes slog, the longest of his career.

Tiley defended the schedule, saying such late matches did not often happen, after Murray's brother Jamie – a doubles specialist playing at Melbourne Park – was among those calling for the only one-night competition at majors.

"If you just put one match at night and there's an injury, you don't have anything for fans or broadcasters," said Tiley.

Tsitsipas rolls on

Back on the court, third seed Stefanos Tsitsipas kept his unbeaten streak this year to set up a last-16 clash with Italian Jannik Sinner.

The 24-year-old Tsitsipas, who is yet to drop a set, clinched his seventh straight win of 2023 by beating Dutchman Tallon Griekspoor 6-2, 7-6 (7/5), 6-3 on Rod Laver Arena.

Tsitsipas – who won all four games at the United Cup leading into the Grand Slam – is the highest seed on the men's side.

His next assignment, for a place in the last eight, is a showdown with 15th-seeded Sinner, who stormed back to crush Hungary's Marton Fucsovics 4-6, 4-6, 6-1, 6-2, 6-0.

Tsitsipas refuses to get carried away as he chases a first major title.

"There are no presents," he warned.

"You should be going after it, creating those opportunities and aiming big within yourself, sometimes surpassing your abilities."

Felix Auger-Aliassime, the Canadian sixth seed, beat Francisco Cerundolo of Argentina in four sets.

Later Friday, two-time Melbourne runner-up Daniil Medvedev of Russia faces dangerous 29th seed Sebastian Korda of the United States.

Hot favorite Novak Djokovic, the record nine-time Australian Open champion, plays 27th seed Grigor Dimitrov on Saturday.