Potro, seeded third, defeated Martin Fischer 7-6 (9-7), 7-6 (7-5) to set up a meeting with Philipp Kohlschreiber.
Kohlschreiber reached the second round with a 6-2, 6-2 win over Marc Gicquel.
In second-round action, Fernando Verdasco defeated Guillermo Canas 6-1, 6-2, qualifier Philipp Petzschner was a 6-3, 6-4 winner over Jan Hernych and Carlos Moya breezed past Eduardo Schwank 6-2, 6-3.
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