Portoroz, Slovenia -- (Sports Network) - Third-seeded Caroline Wozniacki of Denmark and No. 4 Anabel Medina Garrigues both advanced in straight sets in the opening round of the Slovenia Open Monday.

Wozniacki bested Andreja Klepac, 7-5, 6-0, while Medina Garrigues dominated Ekaterina Makarova of Russia, 6-1, 6-3.

Meanwhile, a former champion pulled off one of two upsets on the day. Klara Zakopalova, of the Czech Republic, won the inaugural tournament in 2005 and on Monday beat seventh-seeded Carla Suarez Navarro.

Zakopalova took the 6-4, 6-4 decision over Navarro, of Spain, a quarterfinalist at this year's French Open.

Additionally, Britain's Katie O'Brien fought for a 7-6 (8-6), 4-6, 6-2 victory over fifth-seeded Tsvetana Pironkova, of Bulgaria.

Other winners on Monday were Croatia's Petra Martic, who defeated German Angelique Kerber 7-5, 6-2; Russian Vera Dushevina, who rolled to a 6-3, 6-3 win over Spain's Virginia Ruano Pascual; and Julia Vakulenko of Ukraine, who came back to win 5-7, 6-4, 6-4 against Slovenian wild card Polona Hercog.

Tuesday's first-round play features top-seeded Russian Maria Kirilenko and second-seeded Katerina Srebotnik of Slovenia.