Fourth seed Roberta Vinci was a first-round casualty at the Ladies Open in Biel, Switzerland.
The 34-year-old Italian (pictured), ranked 35 in the world, was beaten 6-4 6-4 in one hour and 13 minutes by Kristyna Pliskova of the Czech Republic.
Romanian eighth seed Monica Niculescu was also sent packing, 6-2 6-2, by 21-year-old Belgian Elise Mertens.
German duo Mona Barthel and Annika Beck got through by beating Slovakia's Jana Cepelova and Swiss Rebeka Masarova respectively.
Great Britain's Heather Watson and Naomi Broady are in first-round action on Tuesday.
