The 26-year-old world No. 8 slumped to a 6-1, 6-2 defeat by veteran Vera Zvonareva on Wednesday, but qualified after the Netherlands' Kiki Bertens, the only player who could have overtaken the Czech, also lost her last-16 tie 6-3, 4-6, 6-3 to Aliaksandra Sasnovich of Belarus in the same tournament. To play with the big tournaments are always hard. Actually, I think it's the first time in my life. She then retired midway through her opening match in Shanghai. But it will be better for my health.
On Wednesday, Halep had announced her withdrawal from the Kremlin Cup with a herniated disc that she suffered during the Wuhan Open earlier this month and that increased the doubts over her participation in the WTA Finals. "I m not ready to compete at this level and I m still sore".
While the top eight singles players will compete in a round-robin format with the victor taking home the Billie Jean King Trophy, the top eight doubles teams will compete in a knockout format for the WTA Finals Martina Navratilova Trophy. Sadly, my back injury hasn't healed the way we hoped it would and I need to put my long-term health first. Romanian did not dare to surgery and planned to finish the season, but back problems have still not allowed the first racket of the world again to go to court.
Halep clinched the year-end top ranking on Monday.
Oil prices slump after large build in US stockpiles
A Chinese man works at a pump jack in PetroChina's Daqing oil field in China's northeastern Heilongjiang province March 18, 2006. Brent crude was down 50 cents a barrel at $80.28 by 1320 GMT.
"The decision was tough for sure", the 27-year-old told WTA Insider.
"I have such great memories from playing in Singapore in 2016 and 2017, and I can't wait to close out the year competing against the other elite players of 2018".
Bertens has won three tournaments this season, including a victory over Halep to claim the Cincinnati Masters title.
Bertens will join Angelique Kerber, Naomi Osaka, Petra Kvitova, Caroline Wozniacki, Sloane Stephens, Karolina Pliskova and Elina Svitolina in Singapore for the $7m showpiece which starts on Sunday.