Novak Djokovic launched his bid for Grand Slam history at the Australian Open on Sunday against an 18-year-old qualifier after fifth seed Andrey Rublev survived a huge scare to progress.
Women's second seed Aryna Sabalenka starts her own title defence later in the evening session on a breezy opening day in Melbourne.
World number one Djokovic is gunning for his 11th Australian Open title and 25th major, which would take him clear of Margaret Court on the all-time list.
The Serbian, with 24 Grand Slams, is already the most-decorated player in the men's game - two clear of the injured Rafael Nadal and four ahead of the retired Roger Federer.
Djokovic came within a whisker of completing a calendar Grand Slam last year, winning three majors and losing a thrilling Wimbledon final to Carlos Alcaraz.
The 36-year-old, who beat Stefanos Tsitsipas in last year's title match in Melbourne, is the hot favourite again and will be fancied to breeze through his opener against Croatia's Dino Prizmic.
The age gap of 18 years and 75 days between the two is the greatest in an Australian Open men's match since Ken Rosewall downed qualifier Cary Stansbury in 1978.
"I'm just hoping I can start the season in a way that I have been starting my seasons, most of my seasons, throughout my career, with a win here in Australia, in Melbourne," said Djokovic.
"It's my favourite place, no doubt."
Earlier, Rublev was cruising against Brazil's Thiago Seyboth Wild - a set ahead and 5-1 up in the second.
He pulled into a 2-0 lead but 78th-ranked Seyboth Wild refused to lie down and breaks in the third and fourth sets set up a tantalising decider against the two-time quarter-finalist.
Rublev failed to convert four match points on Seyboth Wild’s serve at 5-6 in the fifth set but he regained his composure in the decisive tie-break, rallying from 2-5 to triumph on his fifth match point after three hours and 42 minutes.
The Russian collapsed to the ground before letting out a guttural roar, admitting he relaxed in the deciding tie-break, believing he was heading out of the tournament.
"When I was losing 4-1, mentally I gave up and maybe that's what helped me in the end," he said. "I felt it's not my day but then I hit some good serves and good returns."
Jannik Sinner overcame Botic van de Zandschulp 6-4, 7-5, 6-3 in the opening match on Rod Laver Arena.
The Italian fourth seed, one of a new generation of young guns seeking to dethrone Djokovic, did not have it all his own way against the Dutchman but raised his level in the key moments.
It was tougher for former French Open champion Barbora Krejcikova, who survived a scare to beat Japanese wildcard Mai Hontama 2-6, 6-4, 6-3.
The Czech ninth seed, who triumphed at Roland Garros in 2021, dug deep when trailing 3-1 in the second set after losing the opener and eventually turned the tables.
Belarusian star Sabalenka, scheduled to play German qualifier Ella Seidel in the evening session, enjoyed a breakthrough 2023 in which she won in Melbourne, finished runner-up at the US Open and made the semi-finals at Roland Garros and Wimbledon.
Currently ranked number two behind Poland's Iga Swiatek, the 25-year-old said she was in good shape mentally and physically.
Former champion Caroline Wozniacki, granted a wildcard to compete, returns to the scene of her greatest triumph four years after her last appearance at Melbourne Park against Poland's 20th-seed Magda Linette.
The 2018 Australian Open winner, 33, has joined a group of tennis mums juggling on-court commitments with the duties of motherhood, including Elina Svitolina, Angelique Kerber and Naomi Osaka.
Injured former top-10 star Matteo Berrettini pulled out of the tournament on the eve of a blockbuster first-round clash with Tsitsipas, will now face Belgian lucky loser Zizou Bergs.
AFP