Jeremy Chardy was a surprise casualty on the opening day of the German Tennis Championships as he was beaten in three sets by Maximo Gonzalez.
After losing the first set, the Frenchman - seeded fifth for the ATP 500 event on clay in Hamburg - levelled to force a decider and looked on course for round two when he led 5-3 in the third.
However, Gonzalez fought back to force a tie-break and the Argentine prevailed 6-2 2-6 7-6 (7-4).
Fellow seed Nicolas Almagro needed three sets to see off Jan Satral, but Pablo Cuevas had no such problems as the third seed powered past Florian Mayer 6-4 6-3.
The Uruguayan was dominant on his own serve throughout the 73 minutes on court, Cuevas breaking for the third time as he secured a second-round place with his third match point.
Joining the three seeded players in the next phase will be Paul-Henri Mathieu, Nicolas Kicker and Grega Zemlja.
Qualifier Thiago Monteiro joined them by overcoming Mischa Zverev in straight sets in the final match of the day.