Serena Williams says she made “far too many errors to be a professional athlete” as she was knocked out in the Australian Open third round.
The 38-year-old American lost 6-4 6-7 (2-7) 7-5 to China’s 27th seed Wang Qiang.
The defeat means Williams’ quest for a 24th Grand Slam singles title goes on.
“I can’t play like that. I literally can’t do that again. That’s unprofessional. It’s not cool,” Williams said.
The seven-time champion in Melbourne beat 28-year-old Wang in just 44 minutes at the US Open in September when the Chinese player won only one game and 15 points.
That was not reflective of the ability of a player who has been a regular fixture in the world’s top 30 over the past 18 months and reached a career high of 12 after her run in New York.
This time, after initially flinching when serving for the match at 5-4 in the second set, she made amends in spectacular fashion.
Wang had the tools to hurt Williams and continued to execute them in a third set in which most observers would have backed her illustrious opponent to go on and win.
After briefly faltering again as Williams rallied, Wang sealed victory on her third match point.
“I honestly didn’t think I was going to lose that match,” said Williams when asked on her thoughts after levelling at one set all.
Williams had not lost so early in Melbourne since falling to Daniela Hantuchova at the same stage in 2006.
Meanwhile Defending champion Novak Djokovic took only 85 minutes to defeat Yoshihito Nishioka 6-3 6-2 6-2 and reach the fourth round of the Australian Open.
The second seed was ruthless with his serving and also efficient, breaking the Japanese world number 71 five times from six opportunities.
“This was one of my best serving matches,” said the Serb.
Djokovic will play Diego Schwartzman after the Argentine 14th seed beat Dusan Lajovic 6-2 6-3 7-6 (9-7).
The former world number one lost only one point on his own serve in the opening two sets against 24-year-old Nishioka, and he won 93% of points on his first serve.
The 16-time major winner, 32, said he hoped to carry that form into the next match.
He added: “Schwartzman is one of quickest on the ATP Tour. He’s right-handed so I’ll have to have different tactics.
“If my serve is good as it was today then I’ve got a pretty good chance.”
Djokovic paid tribute to former Wimbledon champion Goran Ivanisevic, part of his coaching set-up since last year, for helping improve his action.