Home hopeful Monica Niculescu defeated her regular doubles partner and third seed Klara Koukalova in the first round of the inaugural BRD Bucharest Open.
The Romanian world number 68 took just over an hour to dispatch Czech contender Koukalova 6-3 6-0, setting up a meeting with either France's Alize Lim or Bulgarian qualifier Elitsa Kostova.
Another seeded player to fall at the first hurdle was Germany's Annika Beck (fifth), who won the first set before Lara Arruabarrena fought back to secure a 4-6 6-2 7-6 (7/5) win.
Waiting for Arruabarrena in the next round is Turkey's Cagla Buyukakcay, who beat Veronica Cepede Royg of Paraguay 6-2 6-3.
Eighth seed Polona Hercog and Cristina Dinu also made it through. Slovenia's Hercog was a 6-4 6-3 winner over Georgian-American Anna Tatishvili and Romanian Dinu needed less than an hour to ease past Nadiya Kichenok of Ukraine 6-0 6-3.
Hercog will next play either Katarzyna Piter or Andreea Mitu, while Dinu is preparing to face Kristina Kucova after the Slovakian's 6-3 6-3 victory over sixth seed and compatriot Anna Schmiedlova.
World number three and home favourite Simona Halep, who reached the semi-finals at Wimbledon, will tackle Holland's Indy de Vroome on Tuesday.