RIYADH, Saudi Arabia -- World No.6 Jessica Pegula has withdrawn from the WTA Finals Riyadh presented by PIF with a left knee injury. She will be replaced in the Orange Group by first alternate and World No.9 Daria Kasatkina. 

"Just been kind of struggling with a little bit of an injury," Pegula said, "and for whatever reason, it kind of really flared up this week. Not really sure why. In the few days before practice, it felt really, really good, but it started creeping up right before my first match, and just feel ike I'm not feeling comfortable moving on court."

Kasatkina will face World No.2 Iga Swiatek in the final group stage match on Thursday. Swiatek is looking to rebound from a straight-set loss to Coco Gauff, which dropped her to 1-1 in the Orange Group. 

 The semifinal scenario is this: If Gauff wins, she and Swiatek advance to the semifinals; if Krejcikova defeats Gauff, Krejcikova and Gauff move forward.

Pegula qualified for her third WTA Finals off a strong second half of the season, which saw her surge to titles in Berlin and Toronto and the final in Cincinnati, before breaking through on home soil to make her first Grand Slam final at the US Open. In Riyadh, she suffered straight-set losses to Gauff and Krejcikova to finish the tournament 0-2. 

Earlier in the week, Pegula also announced her withdrawal from next week's Billie Jean King Cup in Malaga, Spain. 

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