Thursday 18 October 2018 14:46, UK
Simona Halep has withdrawn from the WTA Finals because of a lower back injury.
Kiki Bertens - the next highest-ranked player - will now take her place in Singapore for the tournament which runs from October 21-28.
Dutch player Bertens joins Angelique Kerber, Naomi Osaka, Petra Kvitova, Caroline Wozniacki, Sloane Stephens, Karolina Pliskova and Elina Svitolina at the tournament
"Unfortunately, after much discussion with my team and doctors, I have made the decision to withdraw," said Halep.
"I wanted to finish 2018 on a high after such an incredible year, but sadly my back injury hasn't healed the way we hoped it would and I need to put my long-term health first."
Halep clinched the year-end top ranking on Monday after enjoying her best year on tour in 2018.
The Romanian reached the Australian Open final and then won her first Grand Slam title in the French Open a few months later.
But she was forced to retire from her first-round match at the China Open and withdraw from the Kremlin Cup, with a subsequent MRI scan revealing a herniated disc problem.
Bertens has had a breakthrough season at the very top level and recently became the first Dutch player to make the top 10 for more than 20 years.
The 26-year-old, who reached the doubles final in Singapore 12 months ago with Swede Johanna Larsson, said: "I'm very happy with my season and to finish it off at the WTA Finals is the ultimate prize. I have great memories in Singapore."
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We will have coverage of the ATP Finals at London's O2 in November with every match live on Sky Sports.
