Second-seeded Alex Bogomolov Jr. of Russia beat wild card Dino Marcan of Croatia 6-3, 6-1 to advance to the second round of the Zagreb Indoors on Tuesday.
Bogomolov, a quarterfinalist here last year for the U.S., had little trouble with Marcan, who was making his debut on the ATP Tour.
In November, Bogomolov decided to play for the country of his birth, Russia, rather than the United States, where he has lived and trained since 1992.
Another Russian, third-seeded Mikhail Youzhny, also advanced to the second round defeating 2008 champion Sergiy Stakhovsky of Ukraine 6-4, 7-6 (4).
Youzhny wasted two match points at 5-4, allowing Stakhovsky to break and force a tiebreaker.
Sixth-seeded Marcos Baghdatis from Cyprus rallied to beat Lukas Rosol from Czech Republic 4-6, 6-3, 6-3. Baghdatis wasted a 4-0 lead in the first set, and saved three break points at the start of the second.
Eighth-seeded Croat Ivo Karlovic topped Blaz Kavcic from Slovenia 7-6 (2), 6-3.
Poland's Lukasz Kubot defeated Matteo Viola from Italy 6-2, 6-1, while two-time finalist Michael Berrer of Germany ousted Marco Chiudinelli from Switzerland 7-6 (3), 6-1. Berrer next faces top-seeded Croat Ivan Ljubicic. Jurgen Melzer from Austria easily advanced against Philipp Petzschner of Germany, 6-1, 6-3.
