Top-seeded Marin Cilic of Croatia ousted Blaz Kavcic 6-3, 7-6 (5) Friday to set up a Zagreb Indoors semifinal against defending champion Mikhail Youzhny of Russia.
Cilic, a two-time winner in his home event, missed last year's tournament with an injury. He broke Kavcic twice in the opening set and traded breaks with the Slovenian in the second before prevailing in the tiebreaker.
Youzhny reached the semifinals by defeating Croatia's Ivan Dodig 6-3, 6-2, without a break point. The third-seeded Youzhny broke for a 4-2 lead in the first set and took a 4-0 advantage in the second.
Earlier, fourth-seeded Jurgen Melzer of Austria earned the 300th tour win of his career to set up a semifinal against Robin Haase of the Netherlands.
Melzer defeated Lukas Rosol of the Czech Republic 6-4, 6-4 in the quarterfinals, while Haase ousted Philipp Petzschner of Germany 6-4, 3-6, 6-0.
Melzer took a 5-1 lead in the first set and saved four of the five break points he faced in the second, winning the last three games of the match.
Haase served 11 aces and broke Petzschner seven times.