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.