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SINGAPORE - OCTOBER 23: Angelique Kerber of Germany celebrates victory in her singles match against Dominika Cibulkova of Slovakia during day 1 of the BNP Paribas WTA Finals Singapore at Singapore Sports Hub on October 23, 2016 in Singapore. (Photo by Clive Brunskill/Getty Images)

SINGAPORE - OCTOBER 23:  Angelique Kerber of Germany celebrates victory in her singles match against Dominika Cibulkova of Slovakia during day 1 of the BNP Paribas WTA Finals Singapore at Singapore Sports Hub on October 23, 2016 in Singapore.  (Photo by Clive Brunskill/Getty Images)