Defeat for Świątek meant that she also lost her reign as the world number one.

Latvian star Jelena Ostapenko, a French Open winner in 2017, lost the first set 3-6 before dethroning Świątek 6-3, 6-1.

The forehand game was on point for Ostapenko, who now leads the Pole by four wins to zero in the head-to-head.

She will be up against home favourite Coco Gauff, who she defeated in the Australian Open fourth round this year.

After a five-set thriller against Laslo Djere in the previous round, it was a routine night out for Djokovic in the United States, as he reached the quarter-finals with a 6-2, 7-5, 6-4 win against Borna Gojo of Croatia.

"I am satisfied. I like how I entered the match today," Djokovic said after the game.

"Good intensity, great first set.

"Obviously I didn't want to in a way repeat the first set or first couple sets from the third round where I was a little bit flat, I would say, and wasn't bringing the intensity that I brought tonight.

"That made a difference, especially in the first set."

Gauff reached the last eight among women after downing the returning Caroline Wozniacki of Denmark 6-3, 3-6, 6-1.

Taylor Fritz, Frances Tiafoe, and Ben Shelton did the host nation proud, as three men from the United States are in the quarter-finals of the US Open for the first time since 2005.

The last three to do it were Andre Agassi, James Blake, and Robby Ginepri.

An American semi-finalist is guaranteed this year as Tiafoe will face compatriot Shelton.

Shelton despatched countryman Tommy Paul 6-4, 6-3, 4-6, 6-4 to enter the quarters while Tiafoe got the better of Rinky Hijikata of Australia 6-4, 6-1, 6-4.

For the stylish Tiafoe, who dropped only one set this tournament, his explosive serves aided him again as he looks to make it back-to-back semi-finals on home turf.

"It’s a big match. He’s Bugs Bunny. He’s got crazy energy, endless energy," Tiafoe said about his clash with Shelton showdown.

"He’s going to come after me, and I’m going to come after him.

"It's going to be a great battle, we're going to compete really hard.

"Obviously that'll be in the big house [Arthur Ashe Stadium] I plan on being in the semis."

Meanwhile, Fritz eased past Dominic Stricker of Switzerland 7-6, 6-4, 6-4 and is set to face the mighty Djokovic, who is a 23-time Grand Slam champion.

Among women, Karolína Muchová of the Czech Republic registered a 6-3, 5-7, 6-1 win over Wang Xinyu of China and will face Sorana Cîrstea of Romania next.

Cîrstea, the 30th seed here, will be high on confidence after knocking out Olympic gold medallist Belinda Bencic of Switzerland  6-3, 6-3.

In the previous round, the Romanian surprised fourth seed and 2022 Wimbledon champion Elena Rybakina of Kazakhstan.