Two-time Australian Open champion Naomi Osaka became the latest star to pull out of the opening Grand Slam of the year Sunday, leaving the tournament deprived of some of the biggest names in the game. No reason for the Japanese player's withdrawal was given with organizers Tennis Australia tweeting: "We will miss her at AO2023." Ukrainian Dayana Yastremska was promoted to the main draw at Melbourne Park in her absence, AFP reported. Osaka has not played a competitive match since September and reports last week said that, despite being on the official entry list, Tennis Australia were having trouble verifying her whereabouts. The 25-year-old's social media accounts indicated that she had been travelling in Europe with her on-again, off-again boyfriend rapper Cordae. Her no-show was another blow for the tournament starting on January 16 after US Open champion and world number one Carlos Alcaraz withdrew on Friday with a right leg problem. Veteran American Venus Williams will also be missing after picking an injury at last week's Auckland Classic and handing back the wildcard she had been awarded. Open organizers were already reeling from the retirements last year of reigning women's champion Ashleigh Barty and legends Serena Williams and Roger Federer. Former world number one and two-time Grand Slam winner Simona Halep is another not playing after she was provisionally suspended in October for taking the banned substance roxadustat. But nine-time champion Novak Djokovic is back after missing last year's event when he was deported over his vaccination status. Spanish superstar Rafael Nadal, who won the 2022 title in Djokovic's absence, will also line up, taking over the top seeding from Alcaraz. Osaka, the champion in Melbourne in 2019 and 2021, last played at a tournament in Tokyo in September before pulling out with abdominal pain, slumping to 42 in the world rankings. The four-time Grand Slam winner has previously talked about struggles with her mental health and spent all of 2022 outside the top 10, enduring first-round defeats at both the French and US Opens. She withdrew from Wimbledon with an Achilles' injury. Speaking at the Pan Pacific Open in September, she admitted she had gone through "more down than up" in 2022. "This year has been not the best year for me but I've learned a lot about myself," said Osaka, who also won Grand Slams at Flushing Meadows in 2018 and 2020. "Life is ups and downs, and this year was more down than up, but overall I'm pretty happy with where I am now."