The Women's Tennis Association said Thursday that No.1-ranked Simona Halep has withdrawn from the WTA Finals because of a lower back injury.
The Romanian sustained the injury in a training session ahead of the Wuhan Open last month.
"The decision was tough for sure," the 27-year-old told WTA Insider.
"It's always difficult to withdraw from a big tournament. Actually, I think it's the first time in my life. So it was a tough decision but it's better for my health.
"My back is not ok. I didn't practice for the last four weeks. I'm not ready to compete at this level and I'm still sore. It's not easy to go on court and compete at this moment."
Halep's withdrawal means Kiki Bertens has qualified for the final spot, joining Angelique Kerber, Naomi Osaka, Petra Kvitova, Caroline Wozniacki, Sloane Stephens, Karolina Pliskova and Elina Svitolina in Singapore for next week's $7 million tournament.
Halep clinched the year-end top ranking on Monday after her best year on tour, reaching the Australian Open final and then winning her first Grand Slam title in the French Open a few months later.
But she announced at the start of this month that she had an MRI exam after retiring from her first-round match at the China Open, and that a herniated disc problem was found.
"Unfortunately, after much discussion with my team and doctors, I have made the decision to withdraw ... 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," she said.
