The men’s and women’s singles semifinals field is now complete at the 2020 US Open with Serena Williams still in the hunt for a record-equalling 24th Grand Slam singles title and a blockbuster tie between Daniil Medvedev and Dominic Thiem headlining the men’s last four.

American Williams came from a set down to beat Tsvetana Pironkova 6-3 6-2 win in the quarter-finals.

The six-time champion, 38, struggled early on with the variety of shots from the unranked 32-year-old Bulgarian who was in her first tournament in three years.

Williams will now play former world number one Victoria Azarenka, whom she beat in the 2012 and 2013 US Open finals but the American would have to overcome her tendency for sluggish starts if she is to reach her fifth Grand Slam final in three years.

Unseeded Belarusian Victoria Azarenka reached her first Grand Slam semi-final since 2013 with a crushing 6-1 6-0 win over Belgian 16th seed Elise Mertens.

The two-time Australian Open winner has endured difficulties on and off the court since returning to playing after giving birth to son Leo in 2016.

But she was in imperial form against Mertens, breaking her opponent six times in total to complete a stunning victory in only 73 minutes.

The recent Western & Southern champion is on an eleven game unbeaten run but will face an uphill task in Thursday’s semifinal against Williams, whom she has played 22 times but only beaten on four occasions.

Elsewhere, fourth seed Naomi Osaka booked her last four spot with a routine win over world number 93 Shelby Rogers in straight sets.

American Rogers, 27, had upset sixth seed Petra Kvitova in the fourth round but could not match an almost flawless performance from Japan’s 2018 champion.

Although Osaka was broken once in the first set, victory never looked in doubt as she cruised to a 6-3 6-4 win.

The 22-year-old will face American 28th seed Jennifer Brady in the semi-finals.

Brady, 25, reached the last four at a Grand Slam for the first time by beating Kazakh Yulia Putintseva 6-3 6-2.

There will be a first new winner of a men’s Slam since Marin Cilic won the US Open in 2014 but it won’t be one of Daniil Medvedev or Dominic Thiem after both players won their quarterfinals to set up a blockbuster last four tie against each other.

Medvedev, runne-rup last year, saw off fellow Russian Andrey Rublev 7-6 (8-6) 6-3 7-6 (7-5) to set up a meeting with Austrian second seed Thiem.

Medvedev, who was beaten by Rafael Nadal in the 2019 final, was dominant on Arthur Ashe Stadium despite needing a medical timeout in the final set.

The 24-year-old third seed is yet to drop a set in New York this year.

Thiem, 27, booked his place in the US Open last four for the first time with a comprehensive 6-1 6-2 6-4 victory over Australian Alex de Minaur in just over two hours.

German fifth seed Alexander Zverev fought back from a set down to reach his first US Open semi-final by beating a battling Borna Coric.

Zverev, 23, crumbled in the first set as the Croatian 27th seed threatened his hopes of a first Grand Slam title.

But two impressive tie-breaks and a late break in the fourth set gave the German a 1-6 7-6 (7-5) 7-6 (7-1) 6-3 victory.

Zverev will play Spanish 20th seed Pablo Carreno Busta after he beat Canadian 12th seed Denis Shapovalov 3-6 7-6 (7-5) 7-6 (7-4) 0-6 6-3 in a match that lasted more than four hours.

Carreno Busta, 29, who also reached the last four in 2017, said: “I am destroyed, but I am very happy. After this fight it’s tough to say but it’s incredible to be in the semi-final again.”

With Swiss great Roger Federer and Spanish world number two Nadal not competing at Flushing Meadows, and Novak Djokovic – the other member of the ‘big three’ – disqualified, the men’s singles semi-final line-up features four players without a Grand Slam title between them.