Novak Djokovic had a short night in his first singles match in the US since 2021, beating Alejandro Davidovich Fokina in 46 minutes on Wednesday.

The second-ranked Djokovic won the first set 6-4, then two points into the second set, Davidovich Fokina hunched over in pain following a return and retired from the match shortly after.

“Kind of a mixed emotions tonight,” Djokovic said. “Really like Alejandro. Get along really well off the court. We train with each other while in Spain. He told me he has a lower back issue that appeared yesterday. It's unfortunate."

Djokovic, 36, lost in doubles on Tuesday in his return to the country after missing events because of Covid-19 vaccine restrictions.

The winner of a men's-record 23 Grand Slam singles titles, Djokovic will face Frenchman Gael Monfils, who is 0-18 lifetime against him, in the next round.

In the women's draw, top-ranked Iga Swiatek has never reached the quarterfinals of the Cincinnati tournament, but she had an encouraging start to the week, beating American qualifier Danielle Collins 6-1, 6-0.

“Last year, I didn't feel confident in Cincinnati [so] it's big progress for me,” Swiatek said. “I feel like it's going to give me a lot of confidence. I'm happy that I can play better tennis here this year.”

Swiatek will face Zheng Qinwen in the fourth round after the Chinese professional rallied to defeat 43-year-old Venus Williams 1-6, 6-2, 6-1 on Wednesday. (AP)