British number one Heather Watson has advanced to the second round of the WTA Mercury Insurance Open with a 6-3 6-3 victory over Greece's Eleni Daniilidou in Carlsbad, California.

The Guernsey 20-year-old broke her opponent's serve three times and held her own serve throughout.

The win continued Watson's promising preparations for the Olympics, where she will represent Britain in the doubles partnering Laura Robson. Watson claimed the first WTA Tour title of her career on Sunday as she and partner Marina Erakovic beat top seeds Vania King and Jarmila Gajdosova in the final of the Bank of the West Classic.

Seventh seed Yanina Wickmayer retired hurt after losing the first set of her first-round clash with Chan Yung-Jan.

The 22-year-old qualifier from Chinese Taipei edged ahead by taking the first-set tie-break 8-6 before Belgian Wickmayer withdrew citing a back injury.

Chan will now face Watson in round two.

Watson's fellow Briton Anne Keothavong did not fare so well in Carlsbad, though, going down 6-4 6-0 to New Zealand's Erakovic.

Watson later teamed up with Slovakian Janette Husarova in the first round of the doubles competition, and the pair posted a 6-4 7-5 victory over fourth seeds Natalie Grandin and Vladimira Uhlirova.