Polona Hercog made an early exit at the Rio Open as veteran Francesca Schiavone booked her spot in the quarter-finals.
Slovenian fifth seed Hercog went down to Sorana Cirstea 7-5 7-6 (7-3) in one hour, 48 minutes in their second-round clash in Rio de Janeiro on Wednesday.
Hercog served nine double faults against wildcard Cirstea, who capitalised by breaking five times to progress on the clay courts in Brazil.
Joining Romania's Cirstea in the last eight is Italian 35-year-old Schiavone, who advanced with a 6-4 4-6 7-5 victory over Colombian qualifier Mariana Duque-Marino.
Schiavone, the 2010 French Open champion, has slipped to 132nd in the world, but proved too good in the third and deciding set.
In a battle between two qualifiers, Cindy Burger crushed Elitsa Kostova 6-3 6-0 in just over an hour.
American Shelby Rogers also advanced after overcoming Veronica Cepede Royg 7-5 6-4 to make it two wins from as many meetings with the Paraguayan.