Kiki Bertens of the Netherlands slumped to her sixth straight opening-round defeat on Monday, losing to Sorana Cirstea of Romania 6-4, 6-2 at the Generali Ladies.

In Bertens' first match since taking a month off, the French Open semifinalist used a break to go up 4-3 in the opening set but lost nine of the next 11 games and dropped her serve six times.

The 23rd-ranked Bertens, who was seeded sixth, has failed to win a match since reaching the final at Gstaad, Switzerland, in July.

Earlier, Viktorija Golubic of Switzerland defeated eighth-seeded Laura Siegemund of Germany 6-4, 6-2.