Four-time champion Caroline Wozniacki had to battle past Roberta Vinci to book her quarter-final berth at the WTA hardcourt tennis tournament in New Haven.

Denmark's Wozniacki, seeded third this year in the US Open tune-up, saved three match points in the third-set tiebreaker en route to the 6-4, 6-7 (6/8), 7/6 (9/7) win, which saw her reach the quarter-finals for the seventh time in eight appearances on the courts at Yale University.

"I just kept fighting, really," Wozniacki said. "It could have gone either way but thankfully it went my way," she said.

Wozniacki next faces rising French star Caroline Garcia, who booked her quarter-final spot on Tuesday with a win over Magdalena Rybarikova.

Defending champion and second seed Petra Kvitova of Czech Republic lined up a last-eight clash with seventh-seeded Pole Agnieszka Radwanska.

Kvitova rallied to defeat American Madison Keys 4-6, 6-1, 6-2, while Radwanska downed France's Alize Cornet 6-4, 6-2.

Fifth-seeded Czech Karolina Pliskova survived a tough opening set to defeat Ukrainian Olga Savchuk 6-4, 6-1. She next faces Ukrainian Lesia Tsurenko, the lucky loser who replaced injured top seed Simona Halep in the draw and advanced with a second-round win over Barbora Strycova on Tuesday.

The remaining quarter-final, set on Tuesday, will pit fourth-seeded Czech Lucie Safarova against Slovak Dominika Cibulkova.
Source: AFP