Venus Williams was hard-fought quarterfinal winner Friday at the WTA's $2.168 million Western & Southern Open.

The wild card Williams upended third-seeded U.S. Open champion Sam Stosur 6-2, 6-7 (2-7), 6-4 on the hardcourts at the Lindner Family Tennis Center. The former world No. 1 American advanced in 2 hours, 34 minutes despite piling up nine double faults on Day 5.

The 32-year-old seven-time Grand Slam singles champion Williams, who's been slowed mightily by an autoimmune disease over the last couple of seasons, will now appear in her first semifinal in almost two years, or since the 2010 U.S. Open.

Meanwhile, the third round was completed on Friday when 17th-seeded Russian Anastasia Pavlyuchenkova upset sixth-seeded former top-ranked Danish star Caroline Wozniacki 6-4, 6-4 and ninth-seeded Chinese Li Na leveled Swedish qualifier Johanna Larsson 6-2, 6-2. The two matches were suspended/postponed because of rain on Thursday night.

Li was this past Monday's Montreal runner-up to Czech slugger Petra Kvitova.