Last year's runner-up and 2010 champion Viktor Troicki suffered a second-round upset Wednesday at the Kremlin Cup tennis event.
Tunisia's Malek Jaziri upended the third-seeded Serbian Troicki 6-1, 3-6, 6-2 indoors at Olympic Stadium.
Troicki lost to fellow Serb Janko Tipsarevic in last year's Moscow finale.
In other second-round action on Day 3, Czech Lukas Rosol took out sixth-seeded Denis Istomin of Uzbekistan 4-6, 6-4, 6-3 and eighth-seeded Japanese Tatsuma Ito snuck past Russian qualifier Konstantin Kravchuk 7-6 (9-7), 2-6, 6-3. Rosol will face Jaziri in the quarterfinals on Friday.
In opening-round play on Wednesday, French qualifier Edouard Roger-Vasselin defeated Russian wild card Evgeny Donskoy 6-4, 4-6, 6-3; Croat Ivo Karlovic topped Italian Simone Bolelli 6-4, 7-6 (7-4); Italy's Flavio Cipolla handled Russian wild card Teymuraz Gabashvili 6-4, 6-4; and Poland's Jerzy Janowicz dismissed German Benjamin Becker 7-6 (8-6), 6-3.
Top seeds Alexandr Dolgopolov of Ukraine and Italian Andreas Seppi will play second-round matches on Thursday.
This week's champion will take home $121,520.