Jannik Sinner avoided plunging through the US Open trapdoor which claimed Novak Djokovic and Carlos Alcaraz when he stormed into the last 16 on Saturday as fellow world number one Iga Swiatek stayed on course for a second New York triumph.

Australian Open champion Sinner raced past 87th-ranked Christopher O'Connell 6-1, 6-4, 6-2.

The 23-year-old Italian's win came a day after four-time champion Djokovic was sent spinning to his earliest loss in New York in 18 years by Alexei Popyrin.

One day earlier, 2022 winner Alcaraz was defeated in the second round by Dutch journeyman Botic van de Zandschulp.

"Today was great match. I knew I had to play very solid. My serve worked well so I am happy with my performance," said Sinner after firing 15 aces in his 46 winners past outclassed O'Connell of Australia.

Sinner did not face a single break point in his one-hour 53-minute victory which took him into the last 16 for a fourth successive year.

"There have been some upsets in the tournament so let's see what's coming. I'm happy to still be here and play as many matches as possible," added Sinner whose comfortable afternoon on Arthur Ashe Stadium saw tennis legend Serena Williams amongst the spectators.

Sinner will take on 14th seed Tommy Paul for a quarter-final place after the American defeated Canadian qualifier Gabriel Diallo in four sets.

There were 14 breaks of serve in that tie with Diallo, ranked a lowly 143 in the world, undone by 77 unforced errors.

Four-time French Open champion Swiatek was equally dominant as Sinner as the top-seeded Pole eased into the fourth round with a 6-4, 6-2 victory over Russia's Anastasia Pavlyuchenkova.

The 23-year-old didn't face a single break point and will face another Russian, Liudmila Samsonova for a quarter-final place.

"I like the night sessions but it's noisy so I need to focus on my job and stay inside my bubble," said Swiatek who shot a long hard stare at her opponent when a ball was speared towards her early in the second set.

"Anastasia is really powerful, she serves fast so I needed to use my intuition of where the ball was going."

With Djokovic and Alcaraz heading home to Europe, Daniil Medvedev finds himself as the only former champion left in the men's tournament.

The eccentric Russian, seeded five, faces Flavio Cobolli, the world number 31 from Italy.

Medvedev famously shattered Djokovic's bid for a rare calendar Grand Slam when he captured the 2021 title in New York.

This year he was runner-up to Sinner at the Australian Open and made the semis-finals of Wimbledon but is without a tour title since winning the Rome Masters in May last year.

If Medvedev makes the fourth round for the sixth straight year he'll face unseeded Nuno Borges of Portugal who saved three match points in a five-set triumph over Czech teenager Jakub Mensik.

Britain's Jack Draper reached the last 16 for a second successive year by defeating Alcaraz's conqueror Botic van de Zandschulp 6-3, 6-4, 6-2.

- 'I'm a fan' -

Meanwhile, 2023 semi-finalist Karolina Muchova, who knocked out two-time champion Naomi Osaka in the second round, cruised into the last 16 by beating Anastasia Potapova 6-4, 6-2.

She next faces French Open and Wimbledon runner-up Jasmine Paolini, the fifth-seeded Italian, who beat Yulia Putintseva 6-3, 6-4.

Paolini has now made the fourth round of all four Slams this year having previously never got beyond the second round in 16 attempts.

"I'm a fan of her (Muchova). I really love how she plays. She can play every shot, slice, volleys, serve and volleys. She's a very complete player," said Paolini.

US sixth seed Jessica Pegula made the second week for a third successive season by defeating Jessica Bouzas Maneiro 6-3, 6-3.

Pegula next faces Diana Shnaider, the 18th-seeded Russian who made the fourth round of a Slam for the first time by seeing off 37-year-old Sara Errani in straight sets.

Czech Republic's Tomas Machac, ranked 39, also reached the fourth round of a major for the first time by defeating Belgian veteran David Goffin 6-3, 6-1, 6-2.

He will take on Draper for a spot in the quarter-finals.