Her withdrawal means that Kiki Bertens from the Netherlands moves into the eighth and final qualifying spot in the WTA Finals.
"It's always hard to withdraw from a big tournament".
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. Actually, I think it's the first time in my life. In 2014, when she narrowly the French Open crown to Maria Sharapova, Halep's ability to rise to the occasion in her very first major final seemed to indicate that she was herself on the verge of lifting one of the most important trophies in the sport. So it was a tough decision but it's better for my health. "It's not easy to go on court and compete at this moment". "I haven't been training the last four weeks and are not ready to play at this level", - explained the decision of the Romanian tennis player.
As Singapore's five-year association with the multi-million dollar WTA Finals reaches its final leg from Sunday until October 28, exciting times are ahead for boys and girls from the Asia-Pacific region to be part of the popular prelude that is the WTA Future Stars.
Osaka and Stephens are the last two winners of the US Open, the former claiming a stunning breakthrough success last month, while Bertens' place in the field was confirmed earlier this week when Halep pulled out.
The Romanian, who secured the end of year top ranking for a second successive season earlier this week, has made the hard decision not to compete in Singapore to put her "long-term health first".
"Singapore is a special city and I'm sure the fans will enjoy seeing some fantastic women's tennis this week".
The other singles players who will be doing battle for a US$7-million (S$9.6m) prize purse here are Australian Open champion Caroline Wozniacki, US Open victor Naomi Osaka, Wimbledon champion Angelique Kerber, Petra Kvitova, Sloane Stephens, Karolina Pliskova and Elina Svitolina.