NEW HAVEN, Connecticut (AFP) –
Top-seeded Russians Nikolay Davydenko and Svetlana Kuznetsova booked their quarter-final berths Wednesday at the Pilot Pen hardcourt tournament, last tune-up for the US Open.

Davydenko, who heads the men's field, defeated France's Fabrice Santoro 7-5, 6-3 to advance.

French Open champion Kuznetsova clawed her way past Belgian teenager Yanina Wickmayer 6-4, 5-7, 7-6 (7/2).

Defending women's champion and second seed Caroline Wozniacki also advanced to the quarter-finals, defeating rising Russian Anastasia Pavlyuchenkova 6-1, 6-4.

Kuznetsova, who won here two years ago, will play eighth-seeded Amelie Mauresmo of France in the quarter-finals on Thursday.

Kuznetsova admitted she lost focus at times, and said she knows she'll need to do better if she wants a shot at another Grand Slam title in New York.

"I still have it, so I appreciate that I have it, but I have to work on closing out things when I have the chance to," she said.

Wickmayer earned a break in the third set to give herself a chance to serve for the match, but Kuznetsova broke her back and went on to force the tiebreaker.

"I knew at five-all that if I wanted to win the match, I would have to play perfect," Wickmayer said. "And I almost played perfectly, but I guess in the tiebreaker she was just too good for me."

Denmark's Wozniacki will play unseeded Frenchwoman Virginie Razzano, who advanced when fifth-seeded Agnieszka Radwanska of Poland retired. Radwanska won the first set 6-3 but had dropped the second 6-4 when she retired with a hand injury.

In other men's action, seventh-seeded Russian Igor Andreev beat Portuguese qualifier Frederico Gil 6-4, 6-4 and Austrian Jurgen Melzer toppled eighth-seeded Romanian Victor Hanescu 7-6 (7/5), 4-6, 6-1.