U.S. Open | Djokovic, Swiatek advance before China's Zhang shocks Ruud at U.S. Open

The biggest surprise was delivered by Zhang Zhizhen, who stunned last year’s runner-up and world number five Casper Ruud 6-4 5-7 6-2 0-6 6-2 to became the first Chinese man to beat a top-five player since the introduction of the ATP rankings in 1973.

It was business as usual at the U.S. Open on Wednesday with Novak Djokovic and Iga Swiatek marching confidently into the third round but the day ended with a late run of shockers that saw Casper Ruud and Petra Kvitova dumped out of the tournament.

There were plenty of cheers rolling across the sprawling Billie Jean King National Tennis Center all day with Coco Gauff, Taylor Fritz and Frances Tiafoe moving on, as hopes of a homegrown winner continued to build.

But while results followed the form book for much of the day at the year's final Grand Slam, shocks sprung up as the sun went down.

The biggest surprise was delivered by Zhang Zhizhen, who stunned last year's runner-up and world number five Ruud 6-4 5-7 6-2 0-6 6-2 to became the first Chinese man to beat a top-five player since the introduction of the ATP rankings in 1973.

At almost the same time Caroline Wozniacki was claiming the biggest win of her comeback - a 7-5 7-6(5) victory over 11th seed Kvitova.

Earlier, Swiss young gun Dominic Stricker delivered a shock by grinding out a 7-5 6-7(2) 6-7(5) 7-6(6) 6-3 win over Greek seventh seed Stefanos Tsitsipas for his first top-10 win.

Djokovic was prevented from playing in last year's U.S. Open due to being unvaccinated against COVID-19 but has looked right at home on Arthur Ashe Stadium court.