Fourth seed and home favourite Stanislas Wawrinka was bundled out of the Swiss Indoors in Basel at the first-round stage by Russian veteran Nikolay Davydenko.
Davydenko took two hours and 13 minutes to triumph in two tie-break sets 7-6 (9/7) 7-6 (7/3) in a match that saw two breaks of serve by each player in the opening set.
Eighth seed Viktor Troicki was another surprise casualty, the Serbian falling 6-3 6-2 to Bulgaria's Grigor Dimitrov in 73 minutes.
Russian sixth seed Mikhail Youzhny avoided a similar fate with a 6-0 6-2 win over Australian Bernard Tomic, but there was better news for Australia as Matthew Ebden beat Romanian lucky loser Victor Hanescu 6-3 7-6 (7/3).
Swiss wild card Marco Chiudnielli came from behind to beat Spain's Guillermo Garcia-Lopez 5-7 6-3 6-4, while there were also wins for South Africa's Kevin Anderson and American Brian Baker.