The four-time grand slam champion was beaten in three sets – 3-6 7-6 6-4 – by Karolína Plíšková but remained positive after the defeat.
“I’m not really sure if I can be too hard on myself, if that makes sense,” Osaka told reporters.
“I knew going into the match, we had stats on where she serves specifically, but then she changed it up on me.
“I knew that she was going to play really well, and whenever I play her, it’s always three sets. The week is definitely shorter than I wanted it to be, but overall, I think it was a great match and I had a lot of fun.”
Osaka had spent over a year away from the court after opting to prioritize her mental health before becoming a mother in July.
The former world No. 1 made a winning return to tennis on Monday when she beat Germany’s Tamara Korpatsch in her first competitive game in 15 months and took that good form into the first set against Plíšková.
The 26-year-old demonstrated her power to win the opening set and was unlucky to lose the second after a tight tie-break
Plíšková, also returning from an injury layoff, then leaned on her impressive serve to win the deciding set and book her place in the next round.
Osaka, meanwhile, will look ahead to the Australian Open in Melbourne which starts on January 14.
While unsure whether she currently has the game to challenge for a third title Down Under, Osaka said she’s just happy to be playing the sport again.
“I think I’m enjoying myself a lot more, and I also realize there’s a lot of things that aren’t in my control,” she said.
“I feel more aware that I’m playing the best players in the world. Both of us have an opportunity to win.
“I also just think I’ve trained so hard after giving birth that I need to enjoy these moments, and I also think in a way watching [Maria] Sharapova, Serena [Williams] retiring, I know that the tennis lifespan isn’t that long, so I should enjoy it while I can.”
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