Defending champion Pablo Andujar of Spain has advanced to the Swiss Open quarterfinals by beating Dusan Lajovic of Serbia 7-5 6-2.
Fourth-seeded Andujar next faces another former champion on the Gstaad clay courts, two-time winner Thomaz Bellucci of Brazil.
Bellucci beat Stephane Robert of France 6-3 6-2 in their second-round match in the high-end ski resort.
Seeded players advanced in all four matches on a rain-affected Wednesday.
Second-seeded Feliciano Lopez of Spain rallied to win his first singles match since getting married last week.
The 18th-ranked Lopez dropped the first set to 759th-ranked German qualifier Julian Reister in a 2-6 6-4 6-1 victory.
Santiago Giraldo of Colombia, the eighth seed, eased past Marsel Ilhan of Turkey 6-2 6-3.
Meanwhile, Aljaz Bedene has advanced to the quarterfinals of the Hamburg Open by upsetting third-seeded Roberto Bautista Agut 7-6 (2) 7-6 (7).
Bedene will next play eight-seeded Fabio Fognini, who needed three sets to overcome Albert Ramos-Vinolas 6-2 3-6 6-3.
In another upset, sixth-seeded and 2012 Hamburg winner Juan Monaco went out against qualifier Lucas Pouille 6-1 7-5.
Fifth-seeded Pablo Cuevas edged Diego Schwartzman 7-6 (4) 6-4 in a first-round match and Jiri Vesely completed a 3-6 6-1 6-0 win over Andreas Haider-Mauer in a match that had been halted by rain a day earlier.
Vesely will play top-seeded Rafael Nadal in the second round.