As Serena Williams describes her defeat by Wang Qiang at the Australian Open as “unprofessional”, BBC Sport looks at what’s next for the 23-time Grand Slam champion.

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I can’t play like that again, it’s unprofessional – Serena Williams

“I’m way too old to play like this,” Serena Williams declared, as she dissected her earliest Australian Open exit for 14 years.
That was not a nod in the direction of retirement. In fact, she promised to return to the practice court the following day in pursuit of the piece of tennis history which still eludes her.
Friday’s three-set defeat by China’s 27th seed Wang Qiang ended Williams’ hopes of drawing level with Margaret Court’s all-time record of 24 Grand Slam singles titles here in Melbourne.
It was all the more surprising as Wang was not credited with a single winner as she was beaten 6-1 6-0 in just 44 minutes by Williams in September’s US Open quarter-final in New York.
Wang knew she had been completely overpowered, almost embarrassed, so she upped her effort in the gym during pre-season and then cashed in her reward on the Rod Laver Arena.
Williams, in contrast, committed 56 unforced errors. “Unprofessional,” she called it. But is it a sign of the times?
The bad days do tend to grow in number as the years tick by, however great the individual. Roger Federer offered up 82, albeit it in a four-hour-plus match with John Millman which required a fifth-set tie-break to separate them.
A reduced schedule is only to be expected at the age of 38, but Williams seems perennially short of matches. Partly through choice – she has not played a single post-US Open event since 2014 – but also through misfortune.
A series of injuries, most notably to her knee, afforded the American just eight tournaments and 31 matches in 2019. This Australian Open was only her fourth appearance since Wimbledon, and rust will attach itself to even the very best.
Patrick Mouratoglou has coached Serena Williams since 2012
For years, coach Patrick Mouratoglou has repeatedly dangled the magic number of 24 Grand Slam titles to drive Williams’ ambition. Without that goal, she would very likely not still be playing. Without that goal, she might not be a 23-time Grand Slam singles champion.
The target, though, now seems like an albatross around Williams’ neck. She knows the window of opportunity is closing; the pressure is rising.
A 38-year-old, 23-time Grand Slam champion – who is already the oldest female Grand Slam winner of all time – should not have to play with anything to prove.
Federer may experience a similar sensation if Rafael Nadal overtakes or even draws level with his Grand Slam tally of 20 while he is still playing.
As for Williams, her unfinished business could yet be completed. She did, after all, reach the finals of both Wimbledon and the US Open in 2018 and 2019.
I don’t think Friday’s defeat significantly lengthens her odds of winning another Grand Slam. Many opponents now stride onto court for matches against her with far greater conviction, but the women’s game remains phenomenally unpredictable.
Just as Simona Halep and Bianca Andreescu can produce the stunning performances which denied Williams the trophy at Wimbledon and in New York last year, a player with the class and calibre of Naomi Osaka can put in a perplexingly poor performance like the one we saw against Coco Gauff earlier.
Williams’ next appearance will be in the unlikely surroundings of a Fed Cup tie against Latvia in Washington. It is four months until the French Open, which will be followed swiftly by Wimbledon, the Olympics and the US Open.
At this stage of her career, every match counts.