MELBOURNE, Australia (AP) — Two sets and just over an hour of tennis wasn't what Jannik Sinner wanted at Rod Laver Arena for the start of his bid for an Australian Open three-peat.

In his first competitive match since beating Carlos Alcaraz at the ATP Finals in November, Sinner was leading 6-2, 6-1 when No. 93-ranked Hugo Gaston suddenly retired from their match Tuesday night with an undisclosed injury.

“I saw that he was not serving with a very high pace,” Sinner said, but “it’s not the way you want to win the match.”

After signaling he had to quit, Gaston went to a courtside chair and bowed his head into his hands. Sinner went to console him, putting a hand on the Frenchman's shoulder and wishing him a speedy recovery.

For Sinner, it was an anticlimactic return to Melbourne Park's main arena 12 months after clinching back-to-back Australian titles with a win over Alexander Zverev in the final.

He played Alcaraz in the finals of the other three majors, winning at Wimbledon and finishing runner-up at Roland Garros and the U.S. Open, as the so-called Sincaraz rivals extended their dominance of Grand Slam tournaments to a second full year.

Sinner isn't content with evenly splitting the titles with Alcaraz, though. He used his time off to concentrate on adjusting his service motion and tweaking other parts of his game in the search for incremental improvements.

“I’ve put in many, many long days in the off-season trying to become a better tennis player,” No. 2-ranked Sinner said. “But at the end of the day the most important part is to go on court and to enjoy, no? It’s very special to start the season in a night session match here in a Grand Slam, the packed stadium, just trying to do your best.”

Sinner is aiming to become the fourth player to win three consecutive men's titles at the Australian Open.

Osaka's fashion statement

Wearing a wide-brim hat, veil and holding a white parasol as she walked onto Rod Laver Arena for the last night match, Naomi Osaka made a grand entrance.

The four-time major winner went on to beat Antonia Ruzic 6-3, 3-6, 6-4, and later explained the inspiration for her design.

“It’s modeled after a jellyfish,” Osaka said. “I’m just so grateful I get to do the things I love.”

Keys opener

Madison Keys had a tough start to her title defense, struggling early against the offbeat style of Oleksandra Oliynykova before advancing 7-6 (6), 6-1.

Ninth-seeded Keys, playing in her 50th Grand Slam tournament, trailed 4-0 before finding her rhythm.

“Obviously I was very nervous at the start,” Keys said. “As nervous as I was . . . I’m really glad to be back, and that I got through that match.”

Oliynykova's unorthodox shot-making and strong defense kept Keys off balance in the first set.

“I feel like that made things a little extra tricky,” Keys said. “I felt like at the end of the tiebreaker I really kind of found my game and then was able to carry that into the second set.”

Oliynykova gained a lot of attention with her unique body art and ink, and a printed message for Ukraine on a T-shirt she wore in her post-match news conference.

No. 5 Elena Rybakina and No. 10 Belinda Bencic advanced in straight sets, but two women’s seeds were ousted in straight sets early on Day 3, with Janice Tjen upsetting 2021 U.S. Open finalist Leylah Fernandez and Tereza Valentova beating Australia's Maya Joint.

Sloane Stephens, the 2017 U.S. Open champion who had to qualify the season-opening major, lost Karolina Pliskova 7-6 (7), 6-2.

Shelton advances

In a match between left-handers, Ben Shelton, a semifinalist a year ago in Australia, overcame Ugo Humbert 6-3, 7-6 (2), 7-6 (5).

Shelton said it was one of the toughest first-round matches he could have faced, with No. 33 Humbert having the highest ranking of the unseeded players.

He'll next face Australian qualifier Dane Sweeny, who ended the 20th and final Australian Open campaign for 39-year-old Gael Monfils.

Also advancing were No. 5 Lorenzo Musetti, No. 9 Taylor Fritz, 2023 runner-up Stefanos Tsitsipas and Eliot Spizzirri, who beat 19-year-old Joao Fonseca 6-4, 2-6, 6-1, 6-2.

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