LUGANO, Switzerland — Top seed Kristina Mladenovic retired with a back injury in the first round of the weather-affected Samsung Open on Thursday.
Mladenovic was trailing 7-6 (5), 3-2 against Tamara Korpatsch, a German qualifier ranked 157 places below the No. 19 Frenchwoman, when she withdrew.
The clay-court event has been hard hit by rain and two more top players lost first-round matches Thursday.
Fifth seed Svetlana Kuznetsova of Russia was beaten 4-6, 6-3, 6-4 by Germany's Mona Barthel in a match that started Wednesday.
Fourth seed Anett Kontaveit of Estonia also lost 3-6, 6-4, 6-3 to Vera Lapko of Belarus.
Indoor courts have been used at Lugano to get the first round completed. Friday's schedule calls for second-round winners to play their quarterfinals later in the day.