Serena Williams aims to extend her emotional farewell tour at the US Open on Friday as China's Wu Yibing targets a mammoth upset against men's champion Daniil Medvedev.

After knocking out world number two Anett Kontaveit on Wednesday, Williams has fans daring to dream of a fairytale 24th Grand Slam title as she prepares to retire from the sport.

The 40-year-old tennis icon will crank up the hysteria further on Friday if she beats Australia's Ajla Tomljanovic on the Arthur Ashe Stadium court to reach the last 16.

Williams, who barely played for a year before returning to tennis in early August, has been careful to dampen down expectations in what is likely to be her final tournament, dismissing her chances of victory as "fan fantasy."

But the manner of her second round win over Kontaveit, when she reeled off a series of vintage winners to clinch the decisive third set, has left many wondering if the fantasy may yet become reality.

"There are a lot of very strong girls there in the draw but I think if she plays really good tennis, I think she always has a chance to win," was Kontaveit's verdict.

Certainly, Williams' path to what would be a record-equalling 24th Grand Slam singles final has been blown open by the early demise of several higher-ranked rivals.

Three of the top four seeds have already fallen, as well as both of last year's finalists, 2021 champion Emma Raducanu and Canada's Leylah Fernandez.

Williams herself says she is playing without pressure, liberated from the customary expectation that accompanied her Grand Slam campaigns through the years.

"I don't have anything to prove, I don't have anything to win. I have absolutely nothing to lose," Williams said.

Williams' singles campaign will also be boosted by the fact that she is no longer expending energy in the doubles.

The veteran and elder sister Venus were eliminated in the first round on Thursday.

- David v Goliath -

In the men's draw on Friday, Chinese youngster Wu would create one of the biggest shocks in Open history with an upset in his 'David & Goliath' meeting with world number one Medvedev.

The charismatic 22-year-old has been quietly accumulating milestones in New York, becoming the first man from China to win a Grand Slam singles match in 63 years in the opening round, before becoming the first Chinese man ever to reach the third round of the US Open with Wednesday's win over Nuno Borges.

Wu, winner of the US Open junior crown in 2017, hardly played for three years prior to this season due to injury and the Covid-19 pandemic.

In March, his world ranking stood at 1,869, but he has rapidly ascended to 174th since then.

"I think there's more to come," Wu said after his second round defeat of Borges.

"I feel like I have this level to play here in the Grand Slam. Hopefully I keep health, keep playing more Grand Slams."

Wu has been part of a successful contingent of Chinese players at the US Open. Four Chinese women have reached the third round of the tournament, another Grand Slam first.

Two of those women, Wang Xiyu and Zhang Shuai, will be in action on Friday.