The world number eight worked over an ailing Bencic with a comeback 5-7, 6-3, 4-1 victory in one hour and 50 minutes at the Shenzhen Bay Sports Centre. The Swiss struggled with a right leg injury from late in the first set but gamely fought on before calling it a day.

She was the third player to retire mid-match in the tournament following the withdrawals of Kiki Bertens and Bianca Andreescu. World number three Naomi Osaka withdrew from the year-ender before her second match against Ashleigh Barty.

Svitolina will play the winner of the second semi-final between Barty and Karolina Pliskova -- the top two ranked players in the world.

The Ukrainian did not lose a set in the round-robin phase and remains on track to claim a maximum prize of US $4.725 million -- the highest pay cheque in tennis history.

"It's very tough for her," Svitolina said. "I'm going to leave everything on the court (in the final) to try to raise the cup again."

Both players came out firing in a high-quality opening and traded winners but it was the Swiss who impressed with her aggressive approach.

Bencic's freewheeling paid off when a blistering backhand return winner captured the break in the sixth game. But she couldn't capitalise on serve and then later in the set required medical attention on her right hamstring.

Bencic seemed rejuvenated from the treatment and immediately pounced on a loose Svitolina service game in the 12th game to claim the set emphatically with a backhand winner down the line.

Svitolina rediscovered her potent counterpunch in the second set and hit the lines to move around an increasingly frustrated Bencic, who was hampered by her troublesome right leg.

Svitolina cruised through the set to draw level and her momentum continued until Bencic pulled the pin.

The 25-year-old is hoping to end a barren season on a high having not captured a title since last year's triumph in Singapore.