Melbourne, Jan 25 (AFP) Serena Williams suffered her earliest exit from the Australian Open since 2006 but the 23-time Grand Slam champion is not ready to hand over the baton to heir apparent Coco Gauff just yet.

The 38-year-old Williams was downcast but quietly defiant in the aftermath of her shock third-round loss to Wang Qiang on Friday, the 27th-seeded Chinese winning 6-4, 6-7 (2/7), 7-5.

Five hours later, the 15-year-old Gauff pulled off an upset of her own, defeating reigning champion Naomi Osaka 6-3, 6-4 in 67 minutes.

Gauff is the youngest player to beat a defending champion at the Australian Open in the Open era, which began in 1968.

Williams had already won six Grand Slams when Gauff was born in 2004 and there heavily symbolism in the older American passing the younger one on her way out the Melbourne exit door.

But Williams signalled that she will not go quietly in her quest to equal or perhaps surpass the record 24 Grand Slams won by Australia's Margaret Court.

"I feel like I'm on the way up, so we'll see," Williams said, asked if she will be back at Melbourne Park 12 months from now.

"I don't know. I'm not even thinking about anything about not being here."

And in a show of the commitment that has made her one of the greatest players of all time, Williams said: "I'm definitely going to be training tomorrow.

"That's first and foremost, to make sure I don't do this again."

But Chris Evert, an 18-time Grand Slam champion, cast doubt on whether Williams will ever win another Major.

"Her best shot now has to be Wimbledon because she's won that so many times (seven) and her game is, I think, better suited to that surface than any other," the retired former number one told Australian media.

"But I'm just amazed that she's still playing at a high level now at 38 years of age.

"I have a lot of admiration for her, but at the same time the (other) players are only getting better and you wonder how much better she can get."

Williams's last Grand Slam title came three years ago in Melbourne, when she was pregnant with daughter Olympia.

The American great has since reached four Slam finals but failed to win a set in any of them and her last defeat, in the US Open final, was at the hands of 19-year-old Canadian Bianca Andreescu.

- Gauff 'having fun' -

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If Williams is on the way down, albeit reluctantly, Gauff is very much on the way up.

The question now is high and how fast the teenager -- the youngest player in the draw at the Australian Open -- can go.

Gauff and her idol Williams spent time on and off court in pre-season and Williams said in Melbourne that she had been "nowhere near" Gauff's level when the same tender age.

Gauff, who faces American 14th seed Sofia Kenin in the last 16, watched Williams lose while she was waiting for her clash with Japan's two-time Grand Slam champion Osaka.

"I still get nervous when that happens," Gauff said.

The fast-emerging American beat Serena's older sister Venus, a seven-time Major champion, in her Grand Slam debut at Wimbledon last year.

She then repeated the feat in her Melbourne opener, before dumping out Romania's Sorana Cirstea after being a set and 3-0 down.

Gauff was left in tears in the third round at the US Open after a 6-3, 6-0 mauling to then-world number one and title-holder Osaka. She admitted she was overawed by the occasion.

But the tables were turned in Melbourne and it was the Japanese who wilted under the spotlight of a showdown billed as a glimpse into the future of women's tennis.

"Definitely a difference in the mentality entering into the match," Gauff said.

"I was a lot more calm. This match was hyped up, too, but also US Open was hyped up.

"I think now coming into this, I'm just going to have fun, play my best tennis and see what happens." (AFP)

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