Sandra Zahlavova was the biggest casualty of the first qualifying round for the BNP Paribas Open in Indian Wells.
The Czech was beaten 6-4 7-5 by Romania’s Edina Gallovits after making a string of unforced errors.
Also making an early exit was seventh seed and fellow Czech Klara Zakopalova, who went down 6-4 3-6 6-3 to Michelle Larcher De Brito of Portugal.
Second seed Tamarine Tanasugarn breezed past Romania’s Monica Niculescu 6-0 6-1, but third seed Petra Martic had to work harder for a 6-4 4-6 6-4 victory over Anastasia Pivovarova.
British number one Elena Baltacha fought back from a set down to record a 2-6 6-4 6-4 victory over American Julia Boserup.
Arantxa Parra Santonja, seeded fifth, overcame American wildcard Coco Vandeweghe 6-3 6-1 while Japan’s Ayumi Morita, the sixth seed, beat Darya Kustova 6-2 4-6 6-4.
Elsewhere, there were victories for Kai-chen Chang, Kathrin Woerle, Ekaterina Bychkova, Nuria Llagostera Vives, Michaella Krajicek, Pauline Parmentier, Sloane Stephens, Tsvetana Pironkova, Arantxa Rus, Shenay Perry, Viktoriya Kutuzova, Karolina Sprem, Rossana De Los Rios, Yung-jan Chan, Varvara Lepchenko, Akgul Amanmuradova, and Patricia Mayr.