Ekaterina Alexandrova has been called up to replace Keys following Mirra Andreeva, who holds world No 9, decided against participating because of not being fit to compete today, as stated by the Women's Tennis Association.
Current coverage have highlighted concerns about how competitors are facing challenges by the WTA.
Greetings to another day at the WTA Finals. Although both matches offer thrilling action, the primary attraction features Swiatek facing off with Amanda Anisimova.
Their last meeting at the Wimbledon Championships four months ago was remarkably one-sided, with the Polish star achieving a decisive double bagel win. Nevertheless, Anisimova made an impressive recovery shortly after, defeating Swiatek in convincing fashion during the New York tournament.
This crucial encounter marks the final installment of their competitive rivalry, with the victorious player progressing to the next round in Riyadh.
Earlier in the day, Elena Rybakina will compete against Ekaterina Alexandrova instead of Madison Keys. The American player pulled out due to illness in what constitutes a meaningless match, paving the way for the tenth-ranked player to step in. The Kazakh star aims to maintain her unbeaten record, having already beaten both her Polish rival and the American contender to secure her last-four spot.