CANBERRA -- China's top ranked women's tennis player Li Na caused the biggest upset at the Australian Gold Coast tennis tourney as she beat Czech top seed Nicole Vaidisova in straight sets in quarterfinals on Thursday.

Li Na of China plays a forehand return during her match against Nicole Vaidisova of Czechoslovakia at the Australian women's hardcourt tennis championships on the Gold Coast, Australia, Thursday, Jan. 3, 2008. Li won the match 6-3, 6-3. [Agencies]

The 25-year-old Li, who enjoyed an impressive comeback from her rib injury dating back to June 2007, needed only one hour and 13 minutes to beat the 12-ranked teenager 6-3, 6-3.

Li's dark horse journey at the year's first WTA tournament began with a dethroning triumph against the seventh seed and 19-ranked Sybille Bammer from Austria in the opening round.

Li's reward will be a semifinal encounter against either Swiss Patty Schnyder or Franchwoman Amelie Mauresmo.

Converting on the second breaking point in Vaidisova's first service game, Li built up a comfortable 3-0 cushion in the opening set and the 18-year-old Czech sensation managed to hold serve to pull within 3-1.

Next four games saw both players drop serve with Li still keeping pressure on score.

After sealing the first set at 6-3, Li seemed on course for another soaring victory after opening the second set with 3-0 again.

Vaidisova had some chances catching up at 4-3 and leading 30-0 in Li's serve, only for the rampant Li to write off the comeback and storm for a 5-3 lead. Li then served out for the emphatic victory.

Li was 16th in the world in January 2007, her best ever position and the highest by a Chinese player, but suffered a rib injury during a pre-Wimbledon warm-up event.