Alcaraz, Sabalenka into US Open last 16

"The way he plays is unbelievable, the rhythm he has on every shot -- forehand, backhand," Alcaraz said of Wu. "His balls skid a lot on the court and, for me, it's really difficult to control sometimes.

"But I think I stayed there. I played aggressive. I played smart in the toughest moments.

"Wu recovered an early break in each of the first two sets, but Alcaraz pocketed both with breaks in the final games and after saving a pair of break points in the first game of the third the Spaniard rolled home. "I think my level is really good," he said.

"I've got into the rhythm of the competition. I'm getting there. "World number one Sabalenka didn't face a break point in her dismissal of Rakhimova, firing 29 winners with 10 aces.

The numbers didn't tell the whole tale of a match that saw 92nd-ranked Rakhimova challenge Sabalenka in a second-set slugfest. Sabalenka was also unimpressed by the pervasive smell of marijuana -- an increasingly common issue at the US Open -- wafting down from the stands during her match.

"It's a bit tricky to handle that smell while you're trying to compete at your best," said Sabalenka, who at one point complained to the umpire about the issue. Sabalenka, who must repeat as champion to have a chance of remaining number one, next faces Taylor Townsend, the 96th-ranked American who beat 15th-seeded Russian Diana Shnaider 6-2, 6-7 (3/7), 6-3.

Williams sisters lose thriller. With Alcaraz and Sabalenka among the early starters, all eyes on the evening session were on the Williams sisters, partnering in a Grand Slam doubles event for the first time since 2022.

The duo returned to the US Open stage comes after 23-time Grand Slam singles champion Serena came out of a four-year retirement to play at Wimbledon.

But the most famous sister act in tennis -- who won 14 Grand Slam doubles titles together along with three Olympic gold medals -- were beaten 6-3, 6-7 (6/8), 7-6 (10/7) by 14th seeds Chan Hao-ching of Taiwan and Australia's Maya Joint in a marathon three-hour battle.

The Williams' duo had showed flashes of their brilliant best after recovering from losing the first set to level the match after taking the second set on a tie-break. Momentum and a raucous New York crowd appeared to be carrying them towards victory after they sprinted into a 5-0 lead in the third set tie-break.

But Chan and Joint fought back superbly to erase the deficit before clinching victory. Pegula through, Muchova upset.

In other singles action on Friday, 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.

Elsewhere, Ukraine's Marta Kostyuk beat Russian Ekaterina Alexandrova 6-3, 6-2 and American Emma Navarro upset seventh-seeded Czech Karolina Muchova 6-3, 7-5. Back in the men's draw, American 11th seed Frances Tiafoe was a comfortable 6-4, 6-2, 6-4 victor over Monaco's Valentin Vacherot, seeded 22.

Tiafoe's win earned him a last 16 showdown with Russian seventh seed Daniil Medvedev. Medvedev was a similarly unfussy winner over French 26th seed Arthur Rinderknech, easing to a 6-4, 6-4, 6-4 win in just under two hours.

Unseeded former world number three Stefanos Tsitsipas -- whose ranking has plummeted to 53 -- meanwhile toppled 18th seed Jiri Lehecka, 2-6, 6-1, 7-6 (7/3), 6-1 to reach the US Open fourth round for the first time. Tsitsipas will face American eighth seed Ben Shelton in the last 16.

Shelton defeated Canada's Denis Shapovalov 7-6 (7/3), 6-7 (5/7), 6-3, 6-4 in the late match.