Last year's runner-up and this year's top seed Fabio Fognini was a second-round loser Thursday at the St. Petersburg Open tennis event.
Poland's Michal Przysiezny was leading his Italian counterpart 6-3, 5-3 when Fognini retired with a right foot injury on the indoor hardcourts at the St. Petersburg Sports and Concert Complex.
Fognini lost to Slovak Martin Klizan in last year's finale.
In other second-round action involving seeds, No. 4 Russian Dmitry Tursunov took care of qualifier and fellow Russian Konstantin Kravchuk 6-3, 6-0, No. 6 Latvian Ernests Gulbis held off Estonian Jurgen Zopp 6-3, 1-6, 6-3, and No. 7 Czech Lukas Rosol handled Russian wild card Karen Khachanov 6-4, 6-4. Rosol will face Przysiezny in Friday's quarterfinals.
Two other results saw Portuguese Joao Sousa overcome Ukrainian Sergiy Stakhovsky, the 2009 St. Petersburg titlist, 3-6, 6-4, 6-0, and Spaniard Roberto Bautista Agut come back to beat Russian Evgeny Donskoy 2-6, 6-1, 7-6 (7-5). Sousa will meet Tursunov in the quarters, while Bautista Agut will encounter Gulbis.
One other quarterfinal will pit eighth-seeded Denis Istomin of Uzbekistan against Spaniard Guillermo Garcia-Lopez.
The 2013 St. Petersburg titlist will earn $78,000.