Robredo to face Odesnik of U.S. in second round
Robredo, seeded second, beat Poland's Michal Przysiezny 7-5, 6-2.
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"For me, the first match in a tournament is always difficult and it's important not to take much risk," said Davydenko, who won the Warsaw Open in 2006.
The clay-court tournament, previously held in the northern Polish city of Sopot, is the country's only event on the ATP Tour and has a total prize pool of $628,800.
Robredo, who won his second Warsaw title last year, had to work hard in the first set to overcome Przysiezny.
"He was playing very good at the beginning. I had to keep pushing and get the break," said Robredo, who will face American Wayne Odesnik in the second round.
Fourth-seeded Gilles Simon of France lost to Belgian qualifier Christophe Rochus 6-1, 3-6, 6-3. Rochus fell from the top 100 more than a year ago to No. 194 and has moved up to No. 115 with success on the challenger circuit.
Third-seeded Juan Monaco beat Polish wild card Jerzy Janowicz, 6-4, 6-3.
Information from Reuters and The Associated Press was used in this report.