LUXEMBOURG (AP) Second-seeded Caroline Wozniacki withdrew ill from the Luxembourg Open on Thursday, allowing Monica Niculescu of Romania to advance to the semifinals.

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 U.S. qualifier Lauren Davis, who beat Andrea Petkovic of Germany 2-6, 7-5, 6-2.