Zagreb: Defending champion Ivan Ljubicic defeated Stefan Koubek of Austria, 7-6 (5), 6-7 (5), 6-4 on Thursday to advance to the quarterfinals of the Zagreb Open.Ljubicic, who lost in the first round of the Australian Open nine days after winning the Qatar Open, had 28 aces but didn't earn his first break until the final game in a rematch of last year's final."It was a tough match as I expected," Ljubicic said. "I served well, but I don't think I played so bad from the baseline in over two years."Ljubicic foiled several break points in the opening set but served his way out of trouble with two aces in the tiebreak before Koubek conceded with a shot into the net."Had I not served so well, I certainly would have lost today," Ljubicic said.Ljubicic will face Thomas Johansson of Sweden in the quarterfinals. Johansson led Daniele Bracciali 6-3, 1-0 before the Italian withdrew due to an injured shoulder.Fourth-seeded Mikhail Youzhny of Russia defeated Tomas Cakl of the Czech Republic, 6-4, 6-2, to set up an encounter with Marc Gicquel, who defeated fellow Frenchman Fabrice Santoro, 6-4, 3-6, 6-4.Arnaud Clemente of France defeated Czech Lukas Dlouhy, 6-4, 7-6 (5), and will meet No. 2 seed Marcos Baghdatis of Cyprus.Another Frenchman, Michael Llodra, defeated Ivo Karlovic, 6-4, 7-6 (8), and will face Austrian Alexander Peya, who made his first ATP quarterfinal despite having to qualify.