Madrid: China's French Open winner Li Na booked the first of the women's quarter-final places at the Madrid Masters on Wednesday as she defeated 12th seed Angelique Kerber 7-5, 6-4.
Kerber, who will take over as German number one on Monday from the injured Andrea Petkovic, went down in 85 minutes to Li, who is building momentum on clay as she prepares to defend her title at Roland Garros from May 27.
Li reached the Stuttgart quarter-finals last month in her season debut on the surface.
The winner broke three times on the way to victory, where she will await either top seed Victoria Azarenka or Serb Ana Ivanovic.
In the second round on the blue clay of the Caja Magica, Polish fourth seed Agnieszka Radwanska put an end to the 16-match win streak on clay of Sara Errani with a 6-0, 6-1 thrashing in 65 minutes.
Roberta Vinci struck a blow for Italy after Errani's loss, sending out Belgian Yanina Wickmayer 6-1, 6-2. Errani was fresh from the clay title in Budapest at the weekend.
In the men's second round, there was a home win for fifth seed David Ferrer, who beat Czech Radek Stepanek 7-6 (7/4), 6-2.
Barcelona finalist Ferrer worked for just under 90 minutes for his opening win of the week as he tries to improve on the best season of his life.
The 30-year-old has already won a career-best three titles and was defeating Stepanek for the sixth time in nine meetings.
Croatian Marin Cilic overcame eighth seed John Isner 7-6 (7/4), 7-6 (7/3) despite the big American firing 14 aces in his losing effort.
Cilic dodged a bullet with six double-faults including one as he held match points in the second-set tiebreaker.
Frenchman Gael Monfils continued his winning return after more than a month out with an abdominal injury as the 12th seed won - Russian opponent Igor Andreev retiring with a right shoulder injury when he was trailing 6-3, 1-0.
"I'm playing well considering the time off I had," said Monfils. "I need to keep improving, but it's great to be back on court doing what I love."
The flashy Frenchman now faces a stern test against Czech sixth seed Tomas Berdych, who has won both of their previous matches including a Marseille semi-final in February.
Swiss Stanislas Wawrinka's good form on the surface - blue and red it doesn't matter - continued as the Estoril semi-finalist crushed Austrian Juergen Melzer 6-1, 6-4.