Madison Keys' 2025 WTA Finals campaign came to an unfortunate end after the American, citing a viral illness, withdrew from the year-end event hours before her third group stage match against Elena Rybakina. Subsequently, the first alternate, Mirra Andreeva, was requested to fill in for Keys, but the Russian teenager declined. Ultimately, another Russian, Ekaterina Alexandrova, the second alternate, stepped up.Keys began her campaign at the 2025 WTA Finals in Riyadh, Saudi Arabia, with a chastening 1-6, 2-6 loss at the hands of Iga Swiatek on Saturday, November 1. Two days later, the reigning Australian Open champion was beaten again, this time by compatriot Amanda Anisimova in three sets, leaving the American's chances of progressing to the last four hanging by a thread.However, in the immediate aftermath of the conclusion of her contest against Anisimova, it became clear that not all was well with Keys. The 30-year-old, currently ranked seventh in the world, told her WTA top 10 rival that she wasn't feeling well. Subsequently, Keys avoided shaking hands with both Anisimova and the chair umpire, possibly fearing that she was suffering from an underlying viral illness.On Wednesday, November 5, Madison Keys' fears were confirmed. With barely hours to go before the scheduled start of her third group stage outing against the in-form Elena Rybakina, the American withdrew, which eventually led to World No. 10 Ekaterina Alexandrova replacing her. Mirra Andreeva, the first alternate, rejected the chance to replace Keys because the Russian youngster declared herself lacking in match fitness.WTA Finals 2025 marked Madison Keys' return to the year-end event after nine yearsMadison Keys in action at the 2025 WTA Finals (Source: Getty)Madison Keys got her first taste of the WTA Finals by qualifying for the year-end event back in 2016. At the time, the American was just 21, and the rest of the field at the year-end tournament that year included Angelique Kerber, Agnieszka Radwanska, Simona Halep, Karolina Pliskova, Garbine Muguruza, Dominika Cibulkova, and Svetlana Kuznetsova.On that occasion, Keys lost her first two matches before defeating eventual champion Cibulkova in her final group stage outing. However, this wasn't enough to help the American secure progress to the last four.Ahead of her return to the WTA Finals this year, Keys reflected on her 2016 experience at the tournament, as well as her return to it after nine years."That was obviously an amazing experience. It was all of the people that, growing up, were always at the top of the game. So just to be associated with all of them was a huge honor. After that I always wanted to make it back, so being here again, on the flip side of things, is really cool," Keys told the official website of the WTA."It's never too late for anything, I don't think I would have believed that there would be a nine-year gap in the middle of it, but I'm playing some of my best tennis of my career," she added.Madison Keys' WTA Finals withdrawal marks the end of her 2025 tennis season, with the American now set to rest, recover, and then begin preparations for 2026.