St Petersburg - Lukas Lacko of Slovakia and Yen-Hsun Lu of Taiwan both lost in the first round of the St Petersburg Open on Tuesday.
The fifth-seeded Lacko was beaten by Grega Zemlja of Slovenia 6-3, 6-2, while the sixth-seeded Lu lost to Roberto Bautista-Agut of Spain 6-4, 6-2.
Zemlja won five consecutive games in the first set and never faced a break in the second.
"It's my third time, I think, that I was accepted in the main draw directly," said Zemlja, ranked 69th. "It wasn't easy. Maybe it looked easy, but I was fighting throughout the match. I was trying to win very point, every game."
Daniel Gimeno-Traver of Spain advanced to the second round, eliminating Florent Serra of France 7-6 (7/5), 6-2.
Top-seeded Mikhail Youzhny, the 2004 champion and a two-time runner-up, was scheduled to play Vasek Pospisil in a later match.