Poland's Iga Swiatek hits a backhand return to Denmark's Caroline Wozniacki in their ATP-WTA Indian Wells Masters women's quarter-final tennis match at the Indian Wells Tennis Garden in Indian Wells, California, on March 14, 2024. (PHOTO / AFP)

Top seed Iga Swiatek reached the semi-finals at Indian Wells after former world number one Caroline Wozniacki retired with an apparent foot injury early in the second set on Thursday.

Wozniacki started strongly as she raced into a 4-1 lead but she was soon left frustrated as Swiatek produced a barrage of winners to storm back and win the set 6-4.

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The Dane, who returned to the circuit last year after taking a three-year break to start a family, appeared to be troubled with a problem on her right foot at the end of the first set and took a medical time out to get the issue treated.

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However, that failed to improve the situation and she gestured to her opponent that she was unable to continue once Swiatek had taken a 1-0 lead in the second set.

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"I have a huge respect for her and I'm sad she has to go that way I'm sure she will recover and I hope she will be ready for Miami," Swiatek said.

Swiatek, the 2022 champion, will face Ukrainian Marta Kostyuk in the semi-final. Kostyuk defeated Anastasia Potapova 6-0 7-5.