New York (AFP) - Two-time defending champion Aryna Sabalenka out-gunned Kamilla Rakhimova to reach the US Open last 16, with men’s defending champion Carlos Alcaraz aiming to follow on Friday.

Sabalenka didn’t face a break point in a 6-3, 6-4 victory over Rakhimova, firing 29 winners, with 10 aces.

The numbers didn’t tell the whole tale of a match that saw 92nd-ranked Rakhimova push Sabalenka hard in a second-set slugfest.

“She played incredible tennis, she really pushed me so hard in the second set,” Sabalenka said. “I’m super happy that I was able to close this match in straight sets because she’s a fighter.”

Sabalenka, whose world number one ranking is under threat in New York, got off to a strong start, breaking Rakhimova in her first service game and holding her own serve with ease.

Sabalenka didn’t miss a first serve until the seventh game of the contest, pocketing the first set in 35 minutes.

But Uzbekistan’s Rakhimova dialed up the power in the second set, which featured mammoth service holds from each player before Sabalenka gained the crucial break for a 5-4 lead.

Sabalenka, who must repeat as champion to have a chance of remaining number one, next faces either 15th-seeded Russian Diana Shnaider or 96th-ranked American Taylor Townsend.

Shnaider knocked Sabalenka out of the French Open quarter-finals at Roland Garros in June.

Third-seeded American Jessica Pegula, one of the players with a chance to knock Sabalenka off her No. 1 perch, mounted a desperate fightback to beat Canadian Leylah Fernandez 1-6, 6-4, 6-3 in a battle of former finalists.

Pegula struggled early with the varied spin and speeds of the Canadian lefty’s serve.

“I never feel comfortable playing her,” Pegula said. “I’m really glad I was able to find something there, especially in the second set to turn things around.

In other early matches, Ukraine’s Marta Kostyuk beat Russian Ekaterina Alexandrova 6-3, 6-2.

- Williams sisters reunite -

Alcaraz highlighted the afternoon action on Arthur Ashe Stadium, taking on China’s Wu Yibing.

Seeded second as he returns from a four-month injury absence, Alcaraz has found that it’s not only his forehand that got a little rusty.

The 23-year-old admitted that poor decision making contributed when he dropped the first set in a four-set second-round win over Jaime Faria.

He’ll be looking for further improvement on all fronts when he takes on 113th-ranked Wu, the 2017 US Open boys’ champion whose professional trajectory has been disrupted by injury.

The night session features the return to Ashe of a US tennis great as 23-time Grand Slam singles champion Serena Williams teams up with sister Venus in doubles, taking on the 14th-seeded duo of Chan Hao-ching and Maya Joint.

Venus and Serena won two of their 14 Grand Slam doubles titles together at the US Open, where they first competed in 1997.

Their first doubles appearance together in a major since the 2022 US Open comes after 23-time Grand Slam singles champion Serena returned from almost four years away from professional tennis to play at Wimbledon.

A knee injury in her first-round defeat – to Australia’s Joint – scuppered plans for the sisters to play doubles at Wimbledon.