Two-time Australian Open champion Naomi Osaka has become the latest big name to pull out of the upcoming Grand Slam tournament in Melbourne.
No reason was given for the absence of the former world number one, who has openly admitted her struggles with mental health problems in the past couple of years.
Osaka's most recent appearance on the WTA Tour came in the Pan Pacific Open in September, where she retired from her second-round match with Brazil's Beatriz Haddad Maia.
The Japanese player scooped the 2019 and 2021 Australian Open crowns following her maiden major win at the 2018 US Open, and she clinched glory at Flushing Meadows again in 2020.
Williams and Alcaraz will miss out through injury, with the latter sustaining a leg problem in training, and Emma Raducanu's participation is also up in the air after the British number one rolled her ankle at the ASB Classic in Auckland.