Mischa Zverev of Germany advanced to the second round of the Serbia Open on Monday by beating Israel's Dudi Sela 7-6 (4), 3-6, 6-3.
Slovenia's Blaz Kavcic also moved on after beating Tobias Kamke of Germany, 7-6 (0), 6-1.
Serbia's seventh-seeded Janko Tipsarevic was due to face Kei Nishikori from Japan in the third first-round match.
The Serbia Open is run by the family of the No. 2-ranked Novak Djokovic, who opens his clay-court season on Tuesday after 24 consecutive victories this season.