Simona Halep's season is over.
The world No. 1 withdrew from next week's WTA Finals in Singapore due to the herniated disc that also forced her out of this week's Kremlin Cup in Moscow.
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The Roland Garros champion was expected to withdraw following her departure from the Moscow field.
"Unfortunately, after much discussion with my team and doctors, I have made the decision to withdraw from the WTA Finals in Singapore," Halep wrote in a Twitter post. "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."
The 27-year-old Romanian concludes 2018 with a 46-11 record and three titles, including rallying past Sloane Stephens to win her first career Grand Slam at Roland Garros in June.
Halep, who was runner-up to Caroline Wozniacki at the Australian Open, also won Shenzhen and Montreal. Halep lost her final four matches of the season.
Halep's departure sends her Cincinnati conqueror, Kiki Bertens, into the Singapore field.
Bertens, who is No.9 on the Porsche Race to Singapore, will make her WTA Finals debut.
The 26-year-old Bertens, who won three titles and reached the Wimbledon quarterfinals this year, will be the first Dutchwoman to compete at the WTA Finals since big-serving Brenda Schultz-McCarthy in 1997.
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