Christina McHale and Chanelle Scheepers were first-round winners at the $740,000 Mercury Insurance Open tennis event on Tuesday.
The fifth-seeded American McHale defeated Jarmila Gajdosova 7-6 (7-5), 7-5, while the eighth-seeded South African Scheepers posted a 6-2, 7-6 (7-4) victory over Coco Vandeweghe on the hardcourts at La Costa Resort and Spa.
American Vania King dismissed Taipei's Kai-Chen Chang 6-1, 6-4 and Taiwan's Yung-Jan Chan recorded a win over seventh-seeded Yanina Wickmayer, who retired after trailing 7-6 (8-6) following the first set.
Additional wins came for New Zealand's Marina Erakovic, Hungarian Melinda Czink, Britain's Heather Watson and American Melanie Oudin.
This week's top seed is former Wimbledon runner-up Marion Bartoli of France.
The 2012 Carlsbad champ will claim $96,000.