Top-seeded Russian Nikolay Davydenko and fourth-seeded Austrian crowd favorite Jurgen Melzer highlighted Tuesday's second-round winners at the St. Polten International tennis event -- a final clay-court French Open tuneup. The 2003 St. Polten runner-up Davydenko drubbed Dutchman Sjeng Schalken 6-3, 6-1, while Melzer outlasted fellow lefthander, Luxembourg's Gilles Muller, 6-2, 6-7 (5-7), 7-5. Up next for Davydenko will be 1996 runner-up Felix Mantilla, while Melzer will take on Spaniard David Sanchez in the quarterfinals. The Spanish Mantilla upended fifth-seeded Argentine Mariano Puerta 7-6 (7-2), 4-6, 7-5, while Sanchez derailed seventh-seeded Italian Potito Starace 6-4, 6-4. A pair of upsets came in opening-round action on Day 3, as Belgian Christophe Rochus routed second-seeded Thai Paradorn Srichaphan 6-1, 6-3, while German Michael Kohlmann saved six match points to overcome eighth-seeded Czech Tomas Zib 2-6, 7-6 (9-7), 6-4. The surprising Rochus reached his first-ever Masters Series semifinal last week in Hamburg. In other first-round play, Romanian Victor Hanescu outlasted Czech Jan Hernych 4-6, 6-1, 6-3 and Italian Davide Sanguinetti subdued Czech Jiri Vanek 6-4, 6-2.