World No.1 Iga Swiatek moved into her third consecutive BNP Paribas Open semifinal after former World No.1 Caroline Wozniacki retired from their quarterfinal match on Thursday, due to a right foot injury. The final score was 6-4, 1-0, ret.

Swiatek, the 2022 Indian Wells champion, battled back from 4-1 down in the opening set to clinch the one-set lead. Wozniacki, who won the Indian Wells title back in 2011, took a medical time-out for her foot between sets, and the Dane made it only one more game before ending the match.

"I'm hoping that Caroline will be better and she'll be ready for Miami," Swiatek said, after the match. "It's not the best way to win.

"But I'm happy that I played well enough in first set to win it. For sure it was tight. At the beginning we had many longer rallies, so I felt like I needed to be solid and be ready. At the end I'm happy that I used the chances in the last games."

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Champs' clash truncated: It was a sudden conclusion to an anticipated match between two Grand Slam champions. Swiatek and Wozniacki had only played once before; Swiatek won 1-6, 6-3, 6-4 in their previous meeting at Toronto in 2019, when Wozniacki was ranked No.18 and Swiatek No.65.

Wozniacki, who was contesting her first WTA quarterfinal in four years, looked sharp in the opening games, as she sought her first win over a reigning World No.1 since she defeated Simona Halep to win her lone Grand Slam title at the 2018 Australian Open.

The 33-year-old mother-of-two, who returned from a three-year maternity leave last summer, saved three break points in her first service game. Wozniacki then used a strong angled return to break for a 3-1 lead, and a quick consolidation followed, giving Wozniacki the 4-1 lead.

But Swiatek's heavy hitting helped her get the break back two games later, and the top seed also prevailed in a lengthy ninth game, converting her fourth break point of that tussle to lead 5-4.

Swiatek won her fifth straight game with an ace, closing out the set in emphatic fashion before Wozniacki's injury stopped the clash shortly thereafter, following 65 minutes of play.

Kostyuk awaits: Swiatek will take on No.31 seed Marta Kostyuk in Friday's semifinals. Swiatek defeated Kostyuk in their only previous meeting, notching a 6-3, 6-4 victory over the Ukrainian in the Round of 16 at 2021 Roland Garros.

The 21-year-old Kostyuk booked a spot in her first career WTA 1000 semifinal with a 6-0, 7-5 win over No.28 seed Anastasia Potapova on Thursday. It was Kostyuk's first win in three career meetings with Potapova.

"I practiced with [Swiatek] in Doha, I was really looking forward to actually playing her in the match," Kostyuk said, looking ahead to the semis. "I think it will be a great match. 

"I don't know what else to say, because I'm excited, and I played her in Paris three years ago, and it was a bit different match. We were both in different positions. Even more exciting now."

Highlights: Kostyuk def. Potapova

Kostyuk, who reached her first Grand Slam quarterfinal at this year's Australian Open, held a commanding 6-0, 3-0 lead on Thursday before Potapova made the second set a true showdown, coming all the way back to 5-5.

However, Kostyuk righted the ship in the final two games to collect her victory after just 68 minutes. Kostyuk won 54 percent of points returning the Potapova first serve, and 70 percent of points against the Potapova second serve.