Top-seeded Russian Nikolay Davydenko and fourth-seeded Austrian favorite Jurgen Melzer reached the semifinals at the St. Polten International tennis tournament. The 2003 runner-up Davydenko dropped 1996 runner-up Felix Mantilla of Spain 6-3, 7-5, while the lefthanded Melzer came from behind to beat Spaniard David Sanchez 5-7, 6-4, 6-4 at this final clay-court French Open tuneup. Up next for Davydenko will be capable Argentine Jose Acasuso, while Melzer's final four opponent will be surging Belgian Christophe Rochus, a surprise semifinalist at last week's Hamburg Masters. Acasuso and Rochus pulled double-duty on Day 5 after having their second-round matches rained out here on Wednesday. Acasuso opened his day by beating Spaniard Nicolas Almagro 6-4, 6-4 and capped it by handling German Michael Kohlmann 6-2, 7-6 (7-5) in the quarters. Rochus bested Italian Davide Sanguinetti 6-3, 6-3 before stopping Spaniard Guillermo Garcia-Lopez 6-3, 6-4 in the round of eight. In other second-round play, Garcia-Lopez upended sixth-seeded Peruvian Luis Horna 6-1, 6-4 and Kohlmann cut down Romanian Victor Hanescu 6-3, 2-6, 7-6 (7-2). Rain wiped out all of Wednesday's schedule here.