PATTAYA, Thailand — Magdalena Rybarikova of Slovakia upset No. 2-seeded Caroline Wozniacki of Denmark 6-4, 6-1 in the quarterfinals of the Pattaya Open on Friday.

The world's No. 51-ranked player capitalized on the weariness of the Danish teenager, who was back on court less than a day after her second-round win over Australian Open junior champion Ksenia Pervak of Russia.

"This is my best match for this year," Rybarikova said. "I had to play aggressive and served well because she returns well."

It will be the second semifinal of the year for the 20-year-old Rybarikova, who made it to the semis at Hobart in the lead up to the Australian Open.

"It's been a good year for me. I have been working hard and beat some good players," she said.

Her semifinal opponent will be either sixth-seeded Tamarine Tanasugarn of Thailand or Sania Mirza of India.

"Tanasugarn is home player. She plays well on grass and reached the quarterfinal at Wimbledon. For Mirza, she used to be in the top 30. No matter who I play will be tough."