Second-seeded Ekaterina Makarova of Russia beat Alexandra Dulgheru 6-4, 6-2 in the first round of the Grand Prix SAR on Monday, while third-seeded Anna Karolina Schmiedlova of Slovakia was routed 6-0, 6-1 by former champion Kiki Bertens.
The 30th-ranked Makarova had three aces, while Bertens — the Dutch winner of the clay-court tournament in 2012 — broke Schmiedlova's serve six times.
In another upset, Brazilian Teliana Pereira beat sixth-seeded Annika Beck 6-3, 6-1, breaking the German player's serve seven times.
Fifth-seeded Timea Babos of Hungary labored to a 6-3, 6-7 (8), 6-1 win against Polona Hercog, while Sweden's Johanna Larsson beat Donna Vekic of Croatia 6-2, 6-2 and next faces Pereira.
Top-seeded Timea Bacsinszky of Switzerland plays Anna Blinkova of Russia in remaining first round matches on Tuesday.