Venus Williams came back from a set down to beat local hope Zheng Saisai at the Huajin Securities WTA Elite Trophy Zhuhai.
Williams was stunned by the Chinese wildcard in the first set, finding herself 1-5 down and on the receiving end of some impressive shotmaking.
She would go on to lose the set despite a mounting a late comeback, but totally turned the tables from there, dominating the second and third sets for a 4-6, 6-1, 6-1 victory.
"You could see that she played amazing and she really is a future champion," Williams said of her opponent.
"First set, wow, she played so well until the last point. She definitely deserved to get the wildcard into this tournament – she has a lot of talent and there are definitely great things for her in the future."
With two wins from two matches in the group stage, Williams became the first player to qualify for the semi-finals.
Elsewhere, Svetlana Kuznetsova won her first match of the competition after her opponent, Caroline Wozniacki, was forced to retire due to injury while trailing 5-7 2-2.
The Dane revealed she cut her finger with a breadknife prior to the start of the tournament and then injured her wrist as a result of not being able to hold her racket properly.
“It's been a really, really frustrating, s****y second half of the year. Basically just been falling apart physically," she said afterwards.
The day's other result saw Karolina Pliskova defeat Sara Errani 6-0 6-3 to also qualify for the last four.