Michael Berrer of Germany upset top-seeded Ivan Ljubicic 6-4, 6-4 on Wednesday to advance to the quarterfinals of Zagreb Indoors.
Berrer, Last year's finalist, had little trouble as shown by him breaking back immediately in the second set after dropping serve for the only time in the match.
"I played badly," Ljubicic said. "It hurts much more losing at home, but the good thing with tennis is that you don't have to wait long for another chance."
Defending champion Ivan Dodig defeated Marsel Ilhan of Turkey by 7-6 (5), 7-5, and later said he wasn't concerned by the back injury which forced his retirement in the first round of the Australian Open.
"It was more important not to feel the injury during play," Dodig said.
Earlier, Jurgen Melzer of Austria upset fifth-seeded Andreas Seppi 6-2, 6-3 for a spot in the quarterfinals.
Melzer was a late entry and had to play in qualifiers, but has lost just nine games in his first two matches. Melzer — a 2010 semifinalist — served nine aces against Seppi and converted four of his seven break points.
"I am very happy with the way I played so far," he said. "I needed some matches after an early exit in Melbourne, where I lost in the first round. . . . And after many injury problems I had last year now I finally play pain free."
Seventh-seeded Robin Haase from the Netherlands also advanced after rallying to beat Matthias Bachinger from Germany 7-6 (4), 3-6, 6-3.
In the remaining first-round matches, Slovenian wild card Grega Zemlja beat Croat Antonio Veic 7-6 (5), 7-6 (6), Dudi Sela of Israel defeated Andreas Beck of Germany 3-6, 6-3, 6-2, and Guillermo Garcia-Lopez of Spain ousted Daviel Evans of Britain 6-4, 1-6, 6-1.
