Kiki Bertens secured a comeback win, defeating the top-seeded Ashleigh Barty in three sets at the WTA Finals. World No. 1 Ashleigh Barty was stunned by late substitute Kiki Bertens 3-6, 6-3, 6-4 at the WTA Finals. Bertens, who replaced injured Naomi Osaka, won her Red Group encounter after two hours and nine minutes on court.