Luxembourg - Second-seeded Caroline Wozniacki withdrew ill from the Luxembourg Open on Thursday, allowing Monica Niculescu of Romania to advance to the semi-finals.
Niculescu will play third-seeded Kiki Bertens after the Dutchwoman beat Denisa Allertova of the Czech Republic 6-0, 6-4.
Top-seeded Petra Kvitova also advanced by beating eighth-seeded Johanna Larsson of Sweden, 6-2, 6-0.
Kvitova will play US qualifier Lauren Davi, who beat Andrea Petkovic of Germany 2-6, 7-5, 6-2.
Results from the WTA Luxembourg tournament on Thursday (x denotes seeding):
Petra Kvitova (CZE x1) bt Johanna Larsson (SWE x8) 6-2, 6-0
Lauren Davis (USA) bt Andrea Petkovic (GER) 2-6, 7-5, 6-2
Kiki Bertens (NED) bt Denisa Allertova (CZE) 6-0, 6-4
Monica Niculescu (ROM) bt Caroline Wozniacki (DEN x2) - walkover