Amanda Anisimova "embraced the fight" to overcome Iga Swiatek in three sets and join the undefeated Elena Rybakina in the knockout stage of the WTA Finals.

In a winner-takes-all encounter, the Wimbledon and US Open finalist progressed to Friday's semi-finals with a 6-7 (3-7) 6-4 6-2 win over the Polish world number two in Riyadh.

Earlier, Rybakina completed a clean sweep of the Serena Williams Group with a 6-4 6-4 win over Ekaterina Alexandrova, a late replacement for the unwell Madison Keys.

Rybakina, who failed to progress past the fourth round at any of the Grand Slams in 2025, is now on a nine-match winning streak and has dropped just one set at the season-ending event so far.

The leading eight women's players in singles and doubles are competing in Saudi Arabia, where £12m ($15.5m) in prize money will be won.

In the Stefanie Graf Group, world number one Aryna Sabalenka plays defending champion Coco Gauff, while Jessica Pegula faces the already eliminated Jasmine Paolini in Thursday's final round-robin matches.