The St. Petersburg Open lost its second seed on Wednesday when Denis Istomin bowed out of the draw.
Poland's Lukasz Kubot upended the Uzbekistanian Istomin in come-from-behind fashion, 4-6, 6-3, 6-4, on the indoor hardcourts at SCC Peterburgsky.
Three other seeds avoided opening-round upsets, as No. 3 Martin Klizan of the Slovak Republic defeated Russian Mikhail Elgin 6-4, 6-3, No. 4 Fabio Fognini of Italy overcame German Tobias Kamke 4-6, 6-2, 6-3, and No. 8 Jurgen Zopp of Estonia topped Russian qualifier Andrey Kumantsov 6-3, 5-3, retired.
Additional first-round wins came for Russian wild card Teymuraz Gabashvili, Ukrainian Sergiy Stakhovsky, Italians Simone Bolelli and Paolo Lorenzi, and Lithuanian Ricardas Berankis, who was a surprise finalist in Los Angeles in July. Stakhovsky was the St. Petersburg champion in 2009. Bolelli beat the '09 runner-up to Stakhovsky, Argentine Horacio Zeballos, in straight sets on Wednesday.
The second round will be staged on Thursday, including a match for top-seeded long-time Russian crowd favorite Mikhail Youzhny, who will be opposed by American Rajeev Ram.
The former top-10 star Youzhny titled in St. Petersburg in 2004 and was the runner-up here in 2002 and 2010.