MELBOURNE, Australia (AFP) — Alexander Zverev overcame a shaky start before reaching the second round on Sunday's first day of the Australian Open while top-ranked Carlos Alcaraz and Aryna Sabalenka get set to enter the fray.

Also in action later at a hot and sunny Melbourne is 45-year-old Venus Williams, who will become the oldest woman ever at the Grand Slam.

Well beaten in last year's final by Jannik Sinner, the third seed Zverev threatened to implode in losing the first set to Canada's 41st-ranked Gabriel Diallo on a tie-break.

But the 28-year-old recovered from the shock to win 6-7 (1/7), 6-1, 6-4, 6-2 on Rod Laver Arena and next meets home player Alexei Popyrin or Alexandre Muller of France.

"Definitely, when I saw the draw I was not too happy," Zverev said on court of facing 24-year-old Diallo.

"He is someone very young, talented and unbelievably aggressive."

Asked how he reset from his first-set wobble, Zverev said: "I was thinking it can't get worse than that."

Also safely through was seventh-seeded Italian Jasmine Paolini as she outclassed Belarusian qualifier Aliaksandra Sasnovich 6-1, 6-2.

Elina Svitolina, the Ukrainian 12th seed, eased past Cristina Bucsa of Spain 6-4, 6-1.

But the seeds did not have it all their own way, with British qualifier Arthur Fery scoring an upset by taking down 20th seed Flavio Cobolli of Italy, 7-6 (7/1), 6-4, 6-1.

Ukraine's 26th seed Dayana Yastremska was another surprise casualty, losing 6-4, 7-5 to Romania's Elena-Gabriela Ruse.

Later, Spain's Alcaraz embarks on his bid to make a slice of history.

He has won the US Open, Wimbledon and French Open, but the Melbourne Park crown is the one Grand Slam missing from his impressive resume.

The furthest the world number one has gone at the opening major of the year is the quarter-finals and he has made it clear that dethroning rival Sinner as champion is his main aim for 2026.

If he does so, the 22-year-old would surpass compatriot Rafael Nadal to become the youngest man to complete a career Grand Slam, which is winning all four majors.

"I'm just hungry for the title, hungry to do a really good result here," said the six-time major winner.

"I'm just getting ready as much as I can. I'm really excited about the tournament beginning."

Alcaraz launches his title charge against 79th-ranked Australian Adam Walton in the final match of the day on Rod Laver Arena.

Opening the night session on centre court is Sabalenka, who is aiming to win a third Melbourne crown in four years.

The Belarusian suffered a surprise defeat to American Madison Keys in a thrilling final 12 months ago.

Sabalenka, who plays French wildcard Tiantsoa Rakotomanga Rajaonah, triumphed at the Brisbane International last week in an ominous statement of intent.