Third seed Viktor Troicki suffered a shock exit in the second round of the Kremlin Cup as he was beaten 6-1 3-6 6-2 by Malek Jaziri.
The Serbian, who won the Moscow-based event two years ago, won the second set but was handily beaten in the other two by his Tunisian opponent.
Jaziri, ranked 112th in the world, completed his surprise victory in one hour and 41 minutes.
Sixth-seeded Russian Denis Istomin also exited the tournament in the second round as he was beaten 4-6 6-4 by Lukas Rosol of the Czech Republic.
Eight seed Tatsuma Ito of Japan was taken to three sets but held his nerve to take a 7-6 (9-7) 2-6 6-3 over Russia's Konstantin Kravchuk.
In the first round there were wins for Edouard Roger-Vasselin, Ivo Karlovic, Jerzy Janowicz and Flavio Cipolla.