Davydenko has not won consecutive matches since returning to the tour in June after recovering from a wrist injury.
“I didn’t play as I can play,” Davydenko said.
Seppi will face Juan Carlos Ferrero in the semis for the second straight year, after the fourth-seeded Spaniard beat No. 6 Alexandr Dolgopolov of Ukraine 6-1, 6-2.
Melzer played the quarter-final just hours after his second-round match — a 6-1, 6-0 rout of Jan Hajek of the Czech Republic — which was postponed from Thursday because of torrential rain.
■SWISS OPEN
AP, GSTAAD, Switzerland
Top-seeded Mikhail Youzhny lost to 147th-ranked Yuri Schukin of Kazakhstan in the Swiss Open quarter-finals.
The 31-year-old Schukin, who came through qualifying, reached his first career semi-final by defeating the 14th-ranked Russian 6-4, 2-6, 7-5 on Friday.
Schukin will play seventh-seeded Frenchman Richard Gasquet in the semi-finals. Gasquet beat fourth-seeded Albert Montanes of Spain 7-6 (7/5), 6-4.
Two Spaniards will meet in the other semi-final. Second-seeded Nicolas Almagro beat Jeremy Chardy of France, 6-2, 7-6 (7/5), while Daniel Gimeno-Traver had an easy 6-2, 6-4 victory over Igor Andreev of Russia.
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