Late entry Kiki Bertens stunned world number one Ashleigh Barty with a comeback three-set victory to shake-up the season-ending WTA Finals in Shenzhen Tuesday.
All four players can still qualify from Red Group after Belinda Bencic's three-set victory over Petra Kvitova in the later match.
Bertens looked in deep trouble at a set and break down, but turned the tide with ruthless returning and aggressive play at the net to overwhelm a deflated Barty, who could have sealed a spot in the semi-finals with victory.
The world No.10 won 3-6, 6-3, 6-4 in two hours and nine minutes in a see-saw match featuring 12 breaks of serve.
"Of course you're always ready to play, but I did not see it coming today," Bertens said of her late call-up. "In the beginning I was struggling. As the match continued, I felt better and better."
"I was happy that at the end I was able to keep calm."
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