SOPOT, Poland -- Martin Vassallo Arguello of Argentina advanced to the quarterfinals of the Prokom Open on Thursday after top-seeded Nikolay Davydenko retired with a left foot injury while trailing 2-6, 6-3, 2-1.
The defending champion at the clay-court event injured the foot in the first round. The 26-year-old Russian received medical attention before deciding to retire.
"Normally I try to fight to the end, but it was very painful and I may have done even more damage by trying to finish the match," Davydenko said. "Since the beginning of Monday I've had a problem with my left toes. Today that became a problem with my foot."
Also Thursday, second-seeded Tommy Robredo of Spain overcame a poor first set and erratic play to down Steve Darcis of Belgium 1-6, 6-0, 7-5.