Kerber, 30, who won the third Grand Slam title of her career at Wimbledon this year, joins top-ranked Simona Halep who booked her place in the event in August.
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"I have many memories of competing in Singapore, especially reaching the final in 2016 and I'm excited to be back and play in front of the amazing fans," Kerber told the WTA website http://www.wtatennis.com/news/angelique-kerber-secures-second-singles-berth-2018-wta-finals-singapore.
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This is the fifth year that world number three Kerber has qualified for the WTA Finals, which will take place at the Singapore Sports Hub from October 21-28.
The top eight singles players at the $7 million prize money event will face off in a round-robin format with the winner taking home the Billie Jean King Trophy.
The top eight doubles teams will compete for the Martina Navratilova Trophy.
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