Anna Karolina Schmiedlova's long wait for a victory goes on after the top seed was dumped out of the Bol Open by Kristina Kucova in the first round on Wednesday.
Schmiedlova started this season ranked 26 in the world with high hopes of making further strides, but the 21-year-old Slovakian has won only two matches - one of which was in the Fed Cup - in a miserable 2016.
World number 124 Kucova became the latest player to take advantage of Schmiedlova's slump, winning 6-4 6-0 on the Croatian Adriatic island after breaking her beleaguered opponent five times.
Schmiedlova's only other success aside from her Fed Cup win in February came in Sydney back in January.
Zhang Shuai, seeded three, was another of the main contenders to lose in the first round, as the 155th-ranked Ysaline Bonaventure claimed a surprise 6-4 7-6 (7-2) victory.
Fourth seed Nao Hibino also fell at the first hurdle, going down 6-2 6-1 against French qualifier Marine Partaud in the WTA 125K Series tournament.
The sixth seed Kurumi Nara retired at 3-3 in the first set of her opening match against Marina Erakovic, while wildcard Tereza Mrdeza advanced at the expense of fellow Croatian Ani Mijacika.