World number two Iga Swiatek will play Daria Kasatkina on Thursday in her must-win match to stay in the hunt for a spot in the WTA Finals semi-finals after Jessica Pegula withdrew from the tournament with a knee injury.
The sixth-seeded American pulled out, the WTA said on Wednesday, after a 6-3 6-3 defeat by Wimbledon champion Barbora Krejcikova on Tuesday ended her chances of qualifying for the last four in Riyadh.
Pegula has been replaced by first alternate and world number nine Kasatkina, who will face Swiatek in her final match in the orange group.
The Pole will look to rebound from her 6-3 6-4 loss to Coco Gauff and also needs the already-qualified American to beat Krejcikova to advance.
