Barbora Krejcikova grabbed the last semifinal spot at the WTA Finals with a 7-5, 6-4 win over Coco Gauff on Thursday, a result that eliminated second-ranked Iga Swiatek from the season-ending tournament.
Krejcikova completes a last-four lineup that already included top-ranked Aryna Sabalenka, Zheng Qinwen and Gauff.
The winner of the Orange Group, Krejcikova will face Zheng in Friday's semifinals, while Gauff will take on Purple Group winner Sabalenka.
Krejcikova took a tight first set, which lasted 54 minutes, after saving four break points, wrapping it up with a powerful backhand that zipped down the line. Gauff, who had not dropped a set in the finals before Thursday, was hurt by unforced errors, with 23 in the opener.
The second set was once again a close affair, but the Wimbledon champion held her nerve to secure the win in 1 hour, 42 minutes.
"This is a big win for me and really happy with how I played and it was a really good match," the 27-year-old Krejcikova said. "It's tough. It was up and down. ... Being here and reaching the semifinal, it's something unimaginable. I'm really proud of myself, and I'm looking forward to the new challenges."
Krejcikova is the lowest-ranked player to book a spot in the semifinals since Sandrine Testud (14) in 2001.
Swiatek earlier routed alternate Daria Kasatkina 6-1, 6-0 in 51 minutes, the fastest match at the WTA Finals in eight years, but she needed Krejcikova to lose to third-ranked Gauff to advance from the Orange Group. Krejcikova, Gauff and Swiatek all finished at 2-1, and Swiatek was eliminated because she had the worst percentage of sets won.
Kasatkina replaced American Jessica Pegula, who withdrew from the tournament Wednesday because of a left knee injury.
"I'm professional enough to always give 100% no matter what the stakes are," Swiatek said.
Kasatkina is not the first player to be steamrolled at the WTA Finals by Swiatek, who took her tally of 6-0 set wins at the tournament to five, tying Serena Williams' total and now behind only Martina Navratilova (12), Chris Evert (7) and Steffi Graf (7).
The Associated Press and Reuters contributed to this report.
