Naomi Osaka is maintaining a brave face after blowing two match points in a gut-wrenching Australian Open defeat that will send the former world No.1 spiralling down the rankings.

As if relinquishing her Open crown wasn't painful enough, Osaka is projected to plummet to a scarcely believable 84th in the world following Friday night's tense 4-6 6-3 7-6 (10-5) third-round loss to Amanda Anisimova.

Osaka looked in tears after departing Margaret Court Arena but was upbeat in her official post-match press conference at Melbourne Park.

"I'm not God. I can't win every match," she said.

"I think this for me is the biggest step - even though I lost, I think I was really focused throughout the entire match and I didn't have a dip.

"So that's really good, you know.

"Hopefully as the season continues, I'll be able to keep this up, and get even better at it.

"For me, I feel like I grew a lot in this match. The last match I played in New York I had a completely different attitude."

The Japanese superstar only returned to tennis this month from a mental break after the US Open in September.

She withdrew from the French Open after refusing to do any media and then missed Wimbledon altogether.

The four-time major winner also admitted the pressure of being the face of the Tokyo Games might have been too much, Osaka falling short in her quest to medal after lighting the Olympic cauldron.

But the 24-year-old looked mentally refreshed when she arrived in Melbourne, and loomed as Ash Barty's biggest title threat.

Pre-tournament, Osaka described the Open as the "sunshine slam" and was looking to get her career back on track after a tumultuous 2021.

Instead, Osaka's shock loss ends her nine-match winning streak at Melbourne Park, where she also took the title in 2019, and cruelled hopes of a much-anticipated last-16 showdown with Barty.

Barty will instead face Anisimova on Sunday after the 20-year-old world No.60 delivered a fearless performance to send the titleholder packing.

Up 5-4 in the third set, Osaka had match points on Anisimova's serve but couldn't close it out.

Anisimova then got off to a flying start in the match tiebreak, racing to a 5-2 lead, which Osaka was unable to peg back.

Now opportunity once again knocks for Anisimova, who reached the fourth round at the Australian Open in 2019 before becoming the youngest French Open semi-finalist in more than a decade.

But before the 2019 US Open, her father and long-time coach Konstantin, died of a heart attack at the age of 52 and she struggled on the tour with her ranking sliding from a high of world No.21.

She currently has Australian coach Darren Cahill on trial.