Lukas Lacko of Slovakia beat seventh-seeded Robin Haase of the Netherlands 6-4, 6-4 Friday to reach the Zagreb Indoors semifinals.
Lacko next faces the winner of the match between defending champion Ivan Dodig of Croatia and Marcos Baghdatis of Cyprus. Lacko earlier ousted second-seeded Alex Bogomolov Jr. of Russia.
In another quarterfinal, third-seeded Mikhail Youzhny of Russia defeated eighth-seeded Ivo Karlovic of Croatia 7-6 (10), 3-,6 7-6 (6).
Germany's Michael Berrer also advanced, defeating Austria's Jurgen Melzer 5-7, 6-4, 6-4. Berrer, a finalist in 2010 and 2011, rallied after failing to convert five break points in the first set.
"I just feel very comfortable here," Berrer said. "I had lot of respect for Melzer. ... I knew it would be difficult and that I had to be on the top of my game to beat him."