Heather Watson's poor recent form continued with a straight-sets defeat to Anna Karolina Schmiedlova in the J&T Banka Prague Open first round.
Watson remains without a win since defeating Donna Vekic in the quarter-finals of the Hobart International in January - a run of eight successive matches.
The 25-year-old was beaten 6-1 6-3 in one hour and 26 minutes against the in-form Schmiedlova, who won the Claro Open Colsanitas in Bogota two weeks ago.
Watson was broken twice as she slipped 4-0 behind before eventually getting on the board in the fifth game, but dropped the next two to lose the opening set in 37 minutes.
Schmiedlova, who has won all three of her WTA titles on clay, led 2-0 before Watson hit back to break the Slovakian's serve three times in a row, only to hand it back on each occasion.
The 23-year-old then held service in the ninth game for victory.
Fourth seed Daria Gavrilova went out in the first round after retiring in the third set against fellow Australian Sam Stosur.
The world number 24 lost the first set 6-3 and claimed the second 6-4, but that was how it stayed as the 24-year-old was not fit to continue after injuring her foot chasing a drop shot.
Czech eighth seed Katerina Siniakova did reach the next stage, seeing off Andrea Petkovic 6-2 7-6 (7/4)
Natalia Vikhlyantseva and lucky loser Tamara Korpatsch both took care of business in straight sets, besting Carina Witthoeft and Oceane Dodin respectively.
China's Qiang Wang and Ekaterina Alexandrova also avoided the need for a third set, but required first-set tie-breaks in their clashes with Viktoria Kuzmova and Richel Hogenkamp.
At the Morocco Open in Rabat third seed Petra Martic fell at the first hurdle.
Martic came up against a tricky opponent in Kirsten Flipkens and, despite starting well, succumbed to a 3-6 6-2 6-4 defeat. Martic faced a total of 15 break points over two and a quarter hours, saving 10.
Zarina Diyas, seeded sixth, made the same early exit.
Former world number five Sara Errani knocked her out 6-4 6-4 in their first meeting since 2015.
Sara Sorribes Tormo came through against Yulia Putinseva, edging the first set 7-6 (7/4) and following with a 6-0 second.
Croatia's Jana Fett beat American Sachia Vickery 6-3 3-6 6-3 and Johanna Larsson claimed bragging rights in an all-Swedish contest against Rebecca Peterson, winning 2-6 6-3 6-1.