World number one Jannik Sinner reached his first US Open semi-final on Wednesday with a four-set victory over 2021 champion and two-time runner-up Daniil Medvedev.

Jessica Pegula became the fourth American to reach this year's US Open semifinals on Wednesday by stunning world number one Iga Swiatek as Jack Draper broke through to his first Grand Slam last-four.

Sinner is the only top-four player left in the men's draw following the exits of Novak Djokovic, Carlos Alcaraz and Alexander Zverev.

Emma Navarro reached her first Grand Slam semi-final at the US Open on Tuesday with a straight-sets victory over Paula Badosa whose challenge dramatically collapsed.

The 23-year-old Italian is the only man to have made the quarter-finals of all four majors this season.

Top seed Swiatek, who won the title two years ago, showcased her all-court game in a straightforward 6-4, 6-1 win over Russian Liudmila Samsonova to open the evening session at Arthur Ashe Stadium and warned she was only going to improve.

The 20-year-old's exit means Serena Williams remains the last woman to successfully defend the US Open title back in 2014.

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.

Alexei Popyrin insisted that his shock US Open triumph over defending champion Novak Djokovic was "not unbelievable" and that winning his maiden Masters title in Montreal on the eve of the tournament "was way bigger".

Novak Djokovic slumped to his earliest exit at the US Open in 18 years on Friday as a four-set, third round defeat to Alexei Popyrin sparked more questions over his long term future in the sport.

Coco Gauff survived late-match drama to keep her US Open title defence alive with a 3-6, 6-3, 6-3 victory over Elina Svitolina on Friday.

Alcaraz lost 6-1, 7-5, 6-4, ending his bid to become only the third man in the modern era to win the French Open, Wimbledon and US Open in the same season.

Alcaraz, the 2022 champion, is seeded to meet Sinner in the semi-finals.

Djokovic, a four-time champion at the tournament and seeking a record 25th Grand Slam title, was leading 6-4, 6-4, 2-0 when Djere called it quits.

In the middle of the afternoon at Flushing Meadows, the searing heat reached 35 degrees Celsius (95 Fahrenheit).

Ruse, ranked 122nd in the world, pulled off the biggest upset of the tournament so far with her win over the eighth-ranked Krejcikova.

Sinner marked his return to the courts for the first time since it was revealed he had failed two drugs tests, coming back from a set and break down to defeat Mackenzie McDonald at the US Open.

Daniel Evans rallied from 0-4 down in the final set to beat Karen Khachanov in the longest match in US Open history on Tuesday, a five-hour, 35-minute epic on court six.

Midnight matches may be popular with fans but not with old campaigner Novak Djokovic, who bemoaned a late night at the start of his U.S. Open title defence on Monday.

Djokovic arrived on Arthur Ashe Stadium for his 40th career night match at the tournament with two gold bags slung over his shoulder in a nod to his recent Olympic success in Paris.