Spanish duo Fernando Verdasco and David Ferrer came through tricky opening tests at the Swedish Open on Tuesday.
Verdasco - a two-time finalist at the tournament - eventually prevailed 6-4 3-6 6-1 against Italian Lorenzo Sonego in a match that lasted two hours and three minutes.
The seventh seed will next face Pedro Sousa, who defeated Radu Albot 6-4 6-3, for a place in the quarter-finals.
Defending champion Ferrer, seeded fifth for an event he has won three times, saved six of the seven break points he faced in the second set to triumph 6-2 7-5 against ATP Tour debutant Zdenek Kolar.
John Millman needed just 51 minutes to seal his progression, recording a resounding 6-0 6-2 triumph against Guido Andreozzi.
The Ymer brothers experienced mixed fortunes, wild card Mikael beating Denis Istomin in straight sets to progress but sibling Elias lost to Brazilian Thiago Monteiro.
At the Croatia Open Umag, Benoit Paire was an early casualty as the Frenchman - seeded eighth - was beaten 6-1 6-3 by Marton Fucsovics of Hungary.
Joao Sousa was also dumped out in the opening round, the seventh seed from Portugal losing in three sets to Slovenia's Aljaz Bedene.
Fellow seed Robin Haase, however, rallied to avoid defeat in his first match, bouncing back after losing the first set to see off Rogerio Dutra Silva 4-6 7-5 6-3.
