Top-seeded Timea Bacsinszky of Switzerland overcame five breaks of serve to beat Kateryna Kozlova of Ukraine 6-3, 2-6, 6-3 and reach the quarterfinals of the Grand Prix SAR on Wednesday.
Bacsinszky, who is ranked 15th, next plays Johanna Larsson of Sweden, who beat Teliana Pereira of Brazil 6-4, 6-4.
Qualifier Aleksandra Krunic of Serbia — ranked 123rd — upset second-seeded Ekaterina Makarova of Russia 6-2, 6-2 while another qualifier — Marina Erakovic of New Zealand — led 6-4 against seventh-seeded Lesia Tsurenko when the Ukrainian retired.
But No. 5 Timea Babos of Hungary beat Britain's Laura Robson 6-1, 6-2, and No. 8 Yulia Putintseva joined her in the last eight with a 6-0, 6-2 win against Germany's Tatjana Maria.
Kiki Bertens, the 2012 champion, and Pauline Parmentier also progressed.