Venus Williams has reached the semi-finals of the inaugural WTA Elite Trophy in Zhuhai with a three-set win over Zheng Saisai.
Williams is guaranteed to finish top of Group A after she again came from behind to win in China.
Zheng, the world number 75, broke Williams at the first time of asking and then moved 5-1 ahead before Williams began to mount a fightback.
The American could not level the set, though, as Zheng served it out 6-4 to move in front.
However, Williams roared back and lost just two games in the final two sets - 6-1 6-1 - as she booked her place in the last four.
Zheng and Madison Keys's final match of the group will be a dead rubber as both have fallen to Williams.
