Luxembourg - Second-seeded Sloane Stephens of the United States has advanced to the quarter-finals of the Luxembourg Open by beating Yvonne Meusburger of Austria 7-5, 6-4 on Thursday.
Stephens, ranked 12th in the world, has yet to lose a set in Luxembourg and will play Stefanie Voegele on Friday.
The 54th-ranked Swiss player struggled to beat Karolina Pliskova of the Czech Republic 6-1, 3-6, 6-3.
In another second-round match, Karin Knapp of Italy beat Andrea Petkovic of Germany 7-5, 7-5.
Results from fourth day of the WTA Luxembourg Open on Thursday (x denotes seeding):
Karin Knapp (ITA) bt Andrea Petkovic (GER) 7-5, 7-5
Stefanie Voegele (SUI) bt Karolina Pliskova (CZE) 6-1, 3-6, 6-3
Sloane Stephens (USA x2) bt Yvonne Meusburger (AUT) 7-5, 6-4