The former world No.1 was forced to withdraw from the Auckland Classic final on Sunday with an abdominal strain after winning the first set 6-4 against Denmark's Clara Tauson.
She grabbed a double break against Tauson with powerful hitting on both flanks, before dropping serve late in the set.
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Osaka underwent treatment between sets, before signalling her retirement and leaving the court in tears.
It was her second injury-related retirement in as many tournaments, after being forced out of the China Open in October with a back injury.
But Osaka issued a statement saying she was "very optimistic" of playing at Melbourne Park, with the Open getting under way this Sunday.
Osaka won the last of her four grand slam trophies at Melbourne Park in 2021.
"I'm having an MRI today to assess," the 27-year-old said.Â
"I don't feel that it's too serious and I still feel very optimistic about AO."
Giving birth to her daughter Shai in July 2023, Osaka has battled injury and struggled for consistency, with the Auckland decider her first WTA final in almost three years.
But she showed glimpses of her best form en route to the New Zealand trophy match, and broke back into the top 50 in the world rankings on Monday.
In September Osaka linked with Patrick Mouratoglou, the long-time coach of retired great Serena Williams, after splitting with her Belgian mentor Wim Fissette, who steered her to four grand slam titles in their four years working together either side of her maternity leave.
Mouratoglou has already made positive inroads with Osaka, who was unable to advance beyond the quarter-finals in any tournament last year.
Open about her mental health battles, the two-time US Open champion appeared upbeat about her prospects in 2025.
"I've come to the conclusion that what's meant for me is meant for me and maybe certain situations occur to train my mind for what's to come," Osaka posted on Instagram.
"Maybe there's bigger and better things on my path and I just have to continue the journey to encounter them.
"That being said, this is about to be a great year."
