The final set began with a tense opening game, one Zheng clinched with an ace to stop the run of games against her. Three games later, she was back in the lead, striking a fierce backhand return winner to break Rybakina and hold for a 4-1 edge.
With momentum slipping away, Rybakina saved three break points in hopes of staving off a double-break deficit but Zheng earned a fourth with a forehand pass, converting with another forehand winner.
A clean backhand winner got Zheng to match point after squandering a 30-0 lead, and one last big serve got her over the finish line and earned her a maiden win at a WTA Finals. In the end, both women struck 40 unforced errors but Zheng managed more winners, 25 to 19.
Her final match of round-robin play will come against Jasmine Paolini, who she defeated in three sets last month at the Dongfeng Voyah Wuhan Open, while Rybakina will play top seed Sabalenka.
