Caroline Wozniacki has admitted that she will need to be at her best if she is to beat Serena Williams in the quarter-finals of the Olympics.
The Danish eighth seed set up an encounter with the Wimbledon champion following a 6-4 6-2 win over Daniela Hantuchova on Wednesday.
"Serena is playing really well," said Wozniacki. "You definitely have to go out and play your best tennis to beat her."
Wozniacki goes into the contest having won just one of her previous five meetings with the American.
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