Updated

Luxembourg City, Luxembourg (SportsNetwork.com) - Former world No. 1 star Caroline Wozniacki and American Sloane Stephens posted second-round victories Thursday at the Luxembourg Open tennis event.

The top-seeded Wozniacki defeated Romanian Monica Niculescu 6-3, 6-2, while the second-seeded Stephens got past Austrian Yvonne Meusburger 7-5, 6-4 on the indoor hardcourts at Kockelscheuer Sport Centre. Niculescu was the back-to- back runner-up in Luxembourg, including a loss against American Venus Williams in last year's finale.

Wozniacki's quarterfinal opponent on Friday will be eighth-seeded Serb Bojana Jovanovski, while Stephens will take on Swiss Stefanie Voegele.

The 2008 Luxembourg runner-up Wozniacki and Stephens were joined in the quarterfinals by third-seeded Wimbledon runner-up Sabine Lisicki, an easy 6-4, 6-0 winner against Czech qualifier Tereza Smitkova. Lisicki was a Luxembourg finalist back in 2009.

Also on Thursday, Italian Karin Knapp doused German Andrea Petkovic 7-5, 7-5 and the aforementioned Voegele edged out Czech Karolina Pliskova 6-1, 3-6, 6-3.

Friday's other quarterfinals will pit Lisicki against Knapp and German Annika Beck versus Polish qualifier Katarzyna Piter.

The 2013 Luxembourg champion will take home $44,000.