World number one Iga Swiatek went through to the last four at Indian Wells as Caroline Wozniacki retired injured from their quarter-final.

Poland's Swiatek came from 4-1 down to take the first set 6-4 before Denmark's Wozniacki required a medical timeout.

The former world number one played on but managed just one more game, which she lost, before having to pull out.

Swiatek has reached three consecutive semi-finals in California and will take on Ukrainian Marta Kostyuk on Friday.

Kostyuk, the 31st seed, secured a first WTA 1,000 semi-final appearance with a 6-0 7-5 win over Russian 28th seed Anastasia Potapova.

Wozniacki, 33, was enjoying her deepest run at a tournament since returning to the circuit last season having come out of retirement after giving birth to her two children.

"Huge respect for her, and I'm sad that we had to finish that way," Swiatek, 22, said after the match.

US Open champion Coco Gauff takes on Yuan Yue in the last eight later on Thursday.