WTA Finals: Kiki Bertens won 3-6, 6-3, 6-4 in two hours and nine minutes in a see-saw match featuring 12 breaks of serve.
Naomi Osaka, who retired during last year's edition of the WTA Finals with a hamstring injury, had been due to play World No.1 Ashleigh Barty later on Tuesday.
Naomi Osaka maintained her unbeaten record over Petra Kvitova having won their only previous clash in a three-set classic in Melbourne.
Japanese law stipulates that a Japanese with more than one nationality must chose one before turning 22 years old.
China Open: Naomi Osaka fought back from a set down to defeat world number one Ashleigh Barty to clinch the title.
Japanese Naomi Osaka will play world number one Ashleigh Barty of Australia in Sunday's championship match in Beijing.
China Open: Naomi Osaka said that she felt she had been "counted out" after hitting poor form following her Australian Open triumph in January.
Naomi Osaka got tough competition from her Swiss opponent who won the first set 7-5
Serena Williams' coach, Patrick Mouratoglou, insists that all players are coached from the sidelines and it is hypocrisy to deny it exists.
Rafael Nadal disposed of South Korean qualifier Chung Hyeon 6-3, 6-4, 6-2, having benefited from three days off after a second-round walkover.
Rafael Nadal needed barely two hours to see John Millman off 6-3, 6-2, 6-2 at Arthur Ashe Stadium.
Ashleigh Barty, the Australian top seed, engineered her second comeback in as many days, overhauling Maria Sakkari 5-7, 6-2, 6-0.