The singles fields of 56 players have narrowed to the final four, which sets up a sensational semifinal Saturday at the Western & Southern Open. On the men’s side, the top four seeds have reached the semifinals for the first time since 2009, while the women’s final four includes three players who have held the No. 1 ranking and a wild card. Here’s a preview of the matches that will determine who plays for the Rookwood Cup.
 Ashleigh Barty vs. Angelique Kerber
It will be a Wimbledon semifinal rematch when current World No. 1 Ashleigh Barty faces a woman who previously held that ranking when she plays Angelique Kerber in the Western & Southern Open semifinals. Barty is closing in on 100 weeks in the top spot while Kerber was No. 1 for 34 weeks. Both are Major champions, with Barty having won a pair of Grand Slam events while Kerber has won three.
Barty is the top seed in Cincinnati for the second time and is looking to improve on that 2019 result in which she reached the semifinals. The Australian counts Wimbledon as one of her four titles this season.
Kerber is now 17-9 at the Western & Southern Open and is bidding to reach the final for the third time. She previously finished as runner-up to Karolina Pliskova in 2016 and Li Na in 2012. The left-hander picked up her first title in nearly three years earlier this summer on grass courts in her native Germany.
Barty has won three of her five contests against Kerber.
 Karolina Pliskova vs. [WC] Jil Teichmann
Karolina Pliskova’s quest for a second Western & Southern Open title will face its next test when she takes on Jil Teichmann for a spot in the final.
Former World No. 1 Pliskova has reached the finals at two of her last three events – Wimbledon and last week in Toronto. The 2016 Cincinnati champion, she owns 16 career titles.
At No. 76, Teichmann is the lowest ranked Western & Southern Open semifinalist since No. 151 Sloane Stephens in 2017. She is bidding to be the fourth straight unseeded finalist at the event. A two-time title winner, Teichmann is looking to reach her first final since Lexington last August.
This will be the first meeting between Teichmann and Pliskova.
 Daniil Medvedev vs.  Andrey Rublev
The seeds have held on to the top half of the men’s draw, with No. 1 Daniil Medvedev advancing to the semifinals where he will face No. 4 Andrey Rublev. It will be the first all-Russian semifinal in tournament history.
Medvedev, 25, is seeking his second straight title here in Cincinnati, having won the Western & Southern Open as the No. 9 seed in 2019. He’s also seeking to win in consecutive weeks, having taken home the trophy last week in Toronto for third title in 2021 and 12th of his career.
Rublev, 23, was named the ATP’s 2020 Most Improved Player after winning five titles to climb into the Top 10 for the first time. A quarterfinalist here as a qualifier in 2019, he comes to Cincinnati after winning a gold medal in mixed doubles at the Tokyo Olympics (with Anastasia Pavlyuchenkova).
Medvedev has won all four previous meetings against Rublev without having ever dropped a set.
 Stefanos Tsitsipas vs.  Alexander Zverev
The ATP’s 2021 match-wins leader Stefanos Tsitsipas will try to stop Alexander Zverev’s winning streak when the two former ATP Finals champions battle for a spot in the Western & Southern Open final.
Tsitsipas, 23, boasts a 48-13 record in 2021 and has reached the final in three of his last six events, including at the French Open and just last week in Toronto. A semifinalist at the Western & Southern Open in New York last year, Tsitsipas had never won a match in Cincinnati before this week.
Zverev, 24, is playing his first event since claiming the gold medal at the Tokyo Olympics. While winning nine straight matches, he has dropped just one set. The US Open runner-up in 2020, he has won three titles this season.
Tsitsipas owns a 6-2 edge in the head-to-head, including a win in this year’s French Open semifinals, but Zverev was victorious in their last hard court meeting, which came in the Acapulco final in March.