• US' teenage sensation Coco Gauff stunned defending champ Naomi Osaka
  • Serena also suffered a shocking exit at the Australian Open
  • Friday was a mixed day for US tennis fans

US tennis had a mixed day at the Australian Open Friday after Coco Gauff knocked defending champion Naomi Osaka out after Serena Williams’ disappointing loss in the third round.

The 15-year-old promising star needed just 67 minutes before she sealed the match in straight sets. Gauff and Osaka met just last year at the US Open and it was Osaka who was victorious. Gauff avenged that loss Friday in front of pumped-up Rod Laver Arena crowd as she progressed to the fourth round at the ongoing Australian Open.

"I don't know where that came from. Honestly, like, what is my life? Two years ago I lost in the first round in juniors and now I'm here," the teenage sensation said in a post-match interview

"I was telling myself one point at a time and keep fighting. You never know what happens on this court,” added Gauff, who earlier eliminated Venus Williams in the opening round.

Osaka’s loss would have brought diverse emotions for the US supporters. Osaka, who lost the match 6-3, 6-4, held dual citizenship until sometime back. Since she was born in Japan and wanted to represent them at the Tokyo Olympics 2020, she recently gave up her US citizenship.

Serena Williams is a seven-time champion in Melbourne Serena Williams is a seven-time champion in Melbourne Photo: AFP / DAVID GRAY

Earlier in the day, US’ ace tennis player Serena was knocked out of the tournament in Melbourne after losing in the third round.

A frustrated Serena said that she made “far too many errors to be a professional athlete" after her 6-4 6-7 (2-7) 7-5 to China's 27th seed Wang Qiang.

Serena, who was looking to equal Margaret Court’s 24 Grand Slam singles titles by winning the Australia Open, went on to add that she cannot repeat that performance ever again as it is “unprofessional and uncool”.

"I can't play like that. I literally can't do that again. That's unprofessional. It's not cool," Williams said in an interview in Melbourne.

When asked what was she thinking after the match was leveled at one set all, Serena said, "I honestly didn't think I was going to lose that match.”

Further explaining her flaws against the Chinese player, Serena added, “I made a lot of errors. I didn't hit any of those shots in New York or in general in a really long time. I just made far too many errors to be a professional athlete today.”